diff --git a/blockchain/reactor.go b/blockchain/reactor.go
index ae52c773..4543f22a 100644
--- a/blockchain/reactor.go
+++ b/blockchain/reactor.go
@@ -8,6 +8,7 @@ import (
 	"time"
 
 	. "github.com/tendermint/go-common"
+	cfg "github.com/tendermint/go-config"
 	"github.com/tendermint/go-p2p"
 	"github.com/tendermint/go-wire"
 	"github.com/tendermint/tendermint/proxy"
@@ -41,7 +42,7 @@ type consensusReactor interface {
 type BlockchainReactor struct {
 	p2p.BaseReactor
 
-	sw           *p2p.Switch
+	config       cfg.Config
 	state        *sm.State
 	proxyAppConn proxy.AppConnConsensus // same as consensus.proxyAppConn
 	store        *BlockStore
@@ -54,7 +55,7 @@ type BlockchainReactor struct {
 	evsw types.EventSwitch
 }
 
-func NewBlockchainReactor(state *sm.State, proxyAppConn proxy.AppConnConsensus, store *BlockStore, fastSync bool) *BlockchainReactor {
+func NewBlockchainReactor(config cfg.Config, state *sm.State, proxyAppConn proxy.AppConnConsensus, store *BlockStore, fastSync bool) *BlockchainReactor {
 	if state.LastBlockHeight == store.Height()-1 {
 		store.height -= 1 // XXX HACK, make this better
 	}
@@ -69,6 +70,7 @@ func NewBlockchainReactor(state *sm.State, proxyAppConn proxy.AppConnConsensus,
 		timeoutsCh,
 	)
 	bcR := &BlockchainReactor{
+		config:       config,
 		state:        state,
 		proxyAppConn: proxyAppConn,
 		store:        store,
@@ -219,11 +221,14 @@ FOR_LOOP:
 					// We need both to sync the first block.
 					break SYNC_LOOP
 				}
-				firstParts := first.MakePartSet()
+				firstParts := first.MakePartSet(bcR.config.GetInt("block_part_size"))
 				firstPartsHeader := firstParts.Header()
 				// Finally, verify the first block using the second's commit
+				// NOTE: we can probably make this more efficient, but note that calling
+				// first.Hash() doesn't verify the tx contents, so MakePartSet() is
+				// currently necessary.
 				err := bcR.state.Validators.VerifyCommit(
-					bcR.state.ChainID, first.Hash(), firstPartsHeader, first.Height, second.LastCommit)
+					bcR.state.ChainID, types.BlockID{first.Hash(), firstPartsHeader}, first.Height, second.LastCommit)
 				if err != nil {
 					log.Info("error in validation", "error", err)
 					bcR.pool.RedoRequest(first.Height)
diff --git a/config/tendermint/config.go b/config/tendermint/config.go
index 86523473..dfdf4170 100644
--- a/config/tendermint/config.go
+++ b/config/tendermint/config.go
@@ -73,7 +73,8 @@ func GetConfig(rootDir string) cfg.Config {
 	mapConfig.SetDefault("cs_wal_light", false)
 	mapConfig.SetDefault("filter_peers", false)
 
-	mapConfig.SetDefault("block_size", 10000)
+	mapConfig.SetDefault("block_size", 10000)      // max number of txs
+	mapConfig.SetDefault("block_part_size", 65536) // part size 64K
 	mapConfig.SetDefault("disable_data_hash", false)
 	mapConfig.SetDefault("timeout_propose", 3000)
 	mapConfig.SetDefault("timeout_propose_delta", 500)
diff --git a/config/tendermint_test/config.go b/config/tendermint_test/config.go
index 0fe861ad..1751af00 100644
--- a/config/tendermint_test/config.go
+++ b/config/tendermint_test/config.go
@@ -87,6 +87,7 @@ func ResetConfig(localPath string) cfg.Config {
 	mapConfig.SetDefault("filter_peers", false)
 
 	mapConfig.SetDefault("block_size", 10000)
+	mapConfig.SetDefault("block_part_size", 65536) // part size 64K
 	mapConfig.SetDefault("disable_data_hash", false)
 	mapConfig.SetDefault("timeout_propose", 2000)
 	mapConfig.SetDefault("timeout_propose_delta", 500)
diff --git a/consensus/common.go b/consensus/common.go
index 2e4a4dba..02b2c4a4 100644
--- a/consensus/common.go
+++ b/consensus/common.go
@@ -6,7 +6,7 @@ import (
 
 // NOTE: this is blocking
 func subscribeToEvent(evsw types.EventSwitch, receiver, eventID string, chanCap int) chan interface{} {
-	// listen for new round
+	// listen for event
 	ch := make(chan interface{}, chanCap)
 	types.AddListenerForEvent(evsw, receiver, eventID, func(data types.TMEventData) {
 		ch <- data
diff --git a/consensus/common_test.go b/consensus/common_test.go
index 7cb3418c..297b842e 100644
--- a/consensus/common_test.go
+++ b/consensus/common_test.go
@@ -8,9 +8,11 @@ import (
 	"testing"
 	"time"
 
+	. "github.com/tendermint/go-common"
 	cfg "github.com/tendermint/go-config"
 	dbm "github.com/tendermint/go-db"
 	bc "github.com/tendermint/tendermint/blockchain"
+	"github.com/tendermint/tendermint/config/tendermint_test"
 	mempl "github.com/tendermint/tendermint/mempool"
 	sm "github.com/tendermint/tendermint/state"
 	"github.com/tendermint/tendermint/types"
@@ -25,30 +27,36 @@ var config cfg.Config // NOTE: must be reset for each _test.go file
 var ensureTimeout = time.Duration(2)
 
 type validatorStub struct {
+	Index  int // Validator index. NOTE: we don't assume validator set changes.
 	Height int
 	Round  int
 	*types.PrivValidator
 }
 
-func NewValidatorStub(privValidator *types.PrivValidator) *validatorStub {
+func NewValidatorStub(privValidator *types.PrivValidator, valIndex int) *validatorStub {
 	return &validatorStub{
+		Index:         valIndex,
 		PrivValidator: privValidator,
 	}
 }
 
 func (vs *validatorStub) signVote(voteType byte, hash []byte, header types.PartSetHeader) (*types.Vote, error) {
 	vote := &types.Vote{
+		ValidatorIndex:   vs.Index,
+		ValidatorAddress: vs.PrivValidator.Address,
 		Height:           vs.Height,
 		Round:            vs.Round,
 		Type:             voteType,
-		BlockHash:        hash,
-		BlockPartsHeader: header,
+		BlockID:          types.BlockID{hash, header},
 	}
 	err := vs.PrivValidator.SignVote(config.GetString("chain_id"), vote)
 	return vote, err
 }
 
-// convenienve function for testing
+//-------------------------------------------------------------------------------
+// Convenience functions
+
+// Sign vote for type/hash/header
 func signVote(vs *validatorStub, voteType byte, hash []byte, header types.PartSetHeader) *types.Vote {
 	v, err := vs.signVote(voteType, hash, header)
 	if err != nil {
@@ -57,102 +65,29 @@ func signVote(vs *validatorStub, voteType byte, hash []byte, header types.PartSe
 	return v
 }
 
-// create proposal block from cs1 but sign it with vs
-func decideProposal(cs1 *ConsensusState, cs2 *validatorStub, height, round int) (proposal *types.Proposal, block *types.Block) {
+// Create proposal block from cs1 but sign it with vs
+func decideProposal(cs1 *ConsensusState, vs *validatorStub, height, round int) (proposal *types.Proposal, block *types.Block) {
 	block, blockParts := cs1.createProposalBlock()
 	if block == nil { // on error
 		panic("error creating proposal block")
 	}
 
 	// Make proposal
-	proposal = types.NewProposal(height, round, blockParts.Header(), cs1.Votes.POLRound())
-	if err := cs2.SignProposal(config.GetString("chain_id"), proposal); err != nil {
+	polRound, polBlockID := cs1.Votes.POLInfo()
+	proposal = types.NewProposal(height, round, blockParts.Header(), polRound, polBlockID)
+	if err := vs.SignProposal(config.GetString("chain_id"), proposal); err != nil {
 		panic(err)
 	}
 	return
 }
 
-//-------------------------------------------------------------------------------
-// utils
-
-/*
-func nilRound(t *testing.T, cs1 *ConsensusState, vss ...*validatorStub) {
-	cs1.mtx.Lock()
-	height, round := cs1.Height, cs1.Round
-	cs1.mtx.Unlock()
-
-	waitFor(t, cs1, height, round, RoundStepPrevote)
-
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, nil, cs1.ProposalBlockParts.Header(), vss...)
-
-	waitFor(t, cs1, height, round, RoundStepPrecommit)
-
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, cs1.ProposalBlockParts.Header(), vss...)
-
-	waitFor(t, cs1, height, round+1, RoundStepNewRound)
-}
-*/
-
-// NOTE: this switches the propser as far as `perspectiveOf` is concerned,
-// but for simplicity we return a block it generated.
-func changeProposer(t *testing.T, perspectiveOf *ConsensusState, newProposer *validatorStub) *types.Block {
-	_, v1 := perspectiveOf.Validators.GetByAddress(perspectiveOf.privValidator.Address)
-	v1.Accum, v1.VotingPower = 0, 0
-	if updated := perspectiveOf.Validators.Update(v1); !updated {
-		panic("failed to update validator")
-	}
-	_, v2 := perspectiveOf.Validators.GetByAddress(newProposer.Address)
-	v2.Accum, v2.VotingPower = 100, 100
-	if updated := perspectiveOf.Validators.Update(v2); !updated {
-		panic("failed to update validator")
-	}
-
-	// make the proposal
-	propBlock, _ := perspectiveOf.createProposalBlock()
-	if propBlock == nil {
-		panic("Failed to create proposal block with cs2")
-	}
-	return propBlock
-}
-
-func fixVotingPower(t *testing.T, cs1 *ConsensusState, addr2 []byte) {
-	_, v1 := cs1.Validators.GetByAddress(cs1.privValidator.Address)
-	_, v2 := cs1.Validators.GetByAddress(addr2)
-	v1.Accum, v1.VotingPower = v2.Accum, v2.VotingPower
-	if updated := cs1.Validators.Update(v1); !updated {
-		panic("failed to update validator")
+func addVotes(to *ConsensusState, votes ...*types.Vote) {
+	for _, vote := range votes {
+		to.peerMsgQueue <- msgInfo{Msg: &VoteMessage{vote}}
 	}
 }
 
-func addVoteToFromMany(to *ConsensusState, votes []*types.Vote, froms ...*validatorStub) {
-	if len(votes) != len(froms) {
-		panic("len(votes) and len(froms) must match")
-	}
-
-	for i, from := range froms {
-		addVoteToFrom(to, from, votes[i])
-	}
-}
-
-func addVoteToFrom(to *ConsensusState, from *validatorStub, vote *types.Vote) {
-	to.mtx.Lock() // NOTE: wont need this when the vote comes with the index!
-	valIndex, _ := to.Validators.GetByAddress(from.PrivValidator.Address)
-	to.mtx.Unlock()
-
-	to.peerMsgQueue <- msgInfo{Msg: &VoteMessage{valIndex, vote}}
-	// added, err := to.TryAddVote(valIndex, vote, "")
-	/*
-		if _, ok := err.(*types.ErrVoteConflictingSignature); ok {
-			// let it fly
-		} else if !added {
-			fmt.Println("to, from, vote:", to.Height, from.Height, vote.Height)
-			panic(fmt.Sprintln("Failed to add vote. Err:", err))
-		} else if err != nil {
-			panic(fmt.Sprintln("Failed to add vote:", err))
-		}*/
-}
-
-func signVoteMany(voteType byte, hash []byte, header types.PartSetHeader, vss ...*validatorStub) []*types.Vote {
+func signVotes(voteType byte, hash []byte, header types.PartSetHeader, vss ...*validatorStub) []*types.Vote {
 	votes := make([]*types.Vote, len(vss))
 	for i, vs := range vss {
 		votes[i] = signVote(vs, voteType, hash, header)
@@ -160,34 +95,9 @@ func signVoteMany(voteType byte, hash []byte, header types.PartSetHeader, vss ..
 	return votes
 }
 
-// add vote to one cs from another
-// if voteCh is not nil, read all votes
-func signAddVoteToFromMany(voteType byte, to *ConsensusState, hash []byte, header types.PartSetHeader, voteCh chan interface{}, froms ...*validatorStub) {
-	var wg chan struct{} // when done reading all votes
-	if voteCh != nil {
-		wg = readVotes(voteCh, len(froms))
-	}
-	for _, from := range froms {
-		vote := signVote(from, voteType, hash, header)
-		addVoteToFrom(to, from, vote)
-	}
-
-	if voteCh != nil {
-		<-wg
-	}
-}
-
-func signAddVoteToFrom(voteType byte, to *ConsensusState, from *validatorStub, hash []byte, header types.PartSetHeader, voteCh chan interface{}) *types.Vote {
-	var wg chan struct{} // when done reading all votes
-	if voteCh != nil {
-		wg = readVotes(voteCh, 1)
-	}
-	vote := signVote(from, voteType, hash, header)
-	addVoteToFrom(to, from, vote)
-	if voteCh != nil {
-		<-wg
-	}
-	return vote
+func signAddVotes(to *ConsensusState, voteType byte, hash []byte, header types.PartSetHeader, vss ...*validatorStub) {
+	votes := signVotes(voteType, hash, header, vss...)
+	addVotes(to, votes...)
 }
 
 func ensureNoNewStep(stepCh chan interface{}) {
@@ -200,39 +110,6 @@ func ensureNoNewStep(stepCh chan interface{}) {
 	}
 }
 
-/*
-func ensureNoNewStep(t *testing.T, cs *ConsensusState) {
-	timeout := time.NewTicker(ensureTimeout * time.Second)
-	select {
-	case <-timeout.C:
-		break
-	case <-cs.NewStepCh():
-		panic("We should be stuck waiting for more votes, not moving to the next step")
-	}
-}
-
-func ensureNewStep(t *testing.T, cs *ConsensusState) *RoundState {
-	timeout := time.NewTicker(ensureTimeout * time.Second)
-	select {
-	case <-timeout.C:
-		panic("We should have gone to the next step, not be stuck waiting")
-	case rs := <-cs.NewStepCh():
-		return rs
-	}
-}
-
-func waitFor(t *testing.T, cs *ConsensusState, height int, round int, step RoundStepType) {
-	for {
-		rs := ensureNewStep(t, cs)
-		if CompareHRS(rs.Height, rs.Round, rs.Step, height, round, step) < 0 {
-			continue
-		} else {
-			break
-		}
-	}
-}
-*/
-
 func incrementHeight(vss ...*validatorStub) {
 	for _, vs := range vss {
 		vs.Height += 1
@@ -252,12 +129,12 @@ func validatePrevote(t *testing.T, cs *ConsensusState, round int, privVal *valid
 		panic("Failed to find prevote from validator")
 	}
 	if blockHash == nil {
-		if vote.BlockHash != nil {
-			panic(fmt.Sprintf("Expected prevote to be for nil, got %X", vote.BlockHash))
+		if vote.BlockID.Hash != nil {
+			panic(fmt.Sprintf("Expected prevote to be for nil, got %X", vote.BlockID.Hash))
 		}
 	} else {
-		if !bytes.Equal(vote.BlockHash, blockHash) {
-			panic(fmt.Sprintf("Expected prevote to be for %X, got %X", blockHash, vote.BlockHash))
+		if !bytes.Equal(vote.BlockID.Hash, blockHash) {
+			panic(fmt.Sprintf("Expected prevote to be for %X, got %X", blockHash, vote.BlockID.Hash))
 		}
 	}
 }
@@ -268,8 +145,8 @@ func validateLastPrecommit(t *testing.T, cs *ConsensusState, privVal *validatorS
 	if vote = votes.GetByAddress(privVal.Address); vote == nil {
 		panic("Failed to find precommit from validator")
 	}
-	if !bytes.Equal(vote.BlockHash, blockHash) {
-		panic(fmt.Sprintf("Expected precommit to be for %X, got %X", blockHash, vote.BlockHash))
+	if !bytes.Equal(vote.BlockID.Hash, blockHash) {
+		panic(fmt.Sprintf("Expected precommit to be for %X, got %X", blockHash, vote.BlockID.Hash))
 	}
 }
 
@@ -281,11 +158,11 @@ func validatePrecommit(t *testing.T, cs *ConsensusState, thisRound, lockRound in
 	}
 
 	if votedBlockHash == nil {
-		if vote.BlockHash != nil {
+		if vote.BlockID.Hash != nil {
 			panic("Expected precommit to be for nil")
 		}
 	} else {
-		if !bytes.Equal(vote.BlockHash, votedBlockHash) {
+		if !bytes.Equal(vote.BlockID.Hash, votedBlockHash) {
 			panic("Expected precommit to be for proposal block")
 		}
 	}
@@ -331,7 +208,7 @@ func fixedConsensusStateDummy() *ConsensusState {
 	return cs
 }
 
-func newConsensusState(state *sm.State, pv *types.PrivValidator, app tmsp.Application) *ConsensusState {
+func newConsensusStateWithConfig(thisConfig cfg.Config, state *sm.State, pv *types.PrivValidator, app tmsp.Application) *ConsensusState {
 	// Get BlockStore
 	blockDB := dbm.NewMemDB()
 	blockStore := bc.NewBlockStore(blockDB)
@@ -342,10 +219,10 @@ func newConsensusState(state *sm.State, pv *types.PrivValidator, app tmsp.Applic
 	proxyAppConnCon := tmspcli.NewLocalClient(mtx, app)
 
 	// Make Mempool
-	mempool := mempl.NewMempool(config, proxyAppConnMem)
+	mempool := mempl.NewMempool(thisConfig, proxyAppConnMem)
 
 	// Make ConsensusReactor
-	cs := NewConsensusState(config, state, proxyAppConnCon, blockStore, mempool)
+	cs := NewConsensusState(thisConfig, state, proxyAppConnCon, blockStore, mempool)
 	cs.SetPrivValidator(pv)
 
 	evsw := types.NewEventSwitch()
@@ -354,6 +231,10 @@ func newConsensusState(state *sm.State, pv *types.PrivValidator, app tmsp.Applic
 	return cs
 }
 
+func newConsensusState(state *sm.State, pv *types.PrivValidator, app tmsp.Application) *ConsensusState {
+	return newConsensusStateWithConfig(config, state, pv, app)
+}
+
 func randConsensusState(nValidators int) (*ConsensusState, []*validatorStub) {
 	// Get State
 	state, privVals := randGenesisState(nValidators, false, 10)
@@ -363,7 +244,7 @@ func randConsensusState(nValidators int) (*ConsensusState, []*validatorStub) {
 	cs := newConsensusState(state, privVals[0], counter.NewCounterApplication(true))
 
 	for i := 0; i < nValidators; i++ {
-		vss[i] = NewValidatorStub(privVals[i])
+		vss[i] = NewValidatorStub(privVals[i], i)
 	}
 	// since cs1 starts at 1
 	incrementHeight(vss[1:]...)
@@ -371,6 +252,20 @@ func randConsensusState(nValidators int) (*ConsensusState, []*validatorStub) {
 	return cs, vss
 }
 
+func randConsensusNet(nValidators int) []*ConsensusState {
+	genDoc, privVals := randGenesisDoc(nValidators, false, 10)
+	css := make([]*ConsensusState, nValidators)
+	for i := 0; i < nValidators; i++ {
+		db := dbm.NewMemDB() // each state needs its own db
+		state := sm.MakeGenesisState(db, genDoc)
+		state.Save()
+		thisConfig := tendermint_test.ResetConfig(Fmt("consensus_reactor_test_%d", i))
+		EnsureDir(thisConfig.GetString("cs_wal_dir"), 0700) // dir for wal
+		css[i] = newConsensusStateWithConfig(thisConfig, state, privVals[i], counter.NewCounterApplication(true))
+	}
+	return css
+}
+
 func subscribeToVoter(cs *ConsensusState, addr []byte) chan interface{} {
 	voteCh0 := subscribeToEvent(cs.evsw, "tester", types.EventStringVote(), 1)
 	voteCh := make(chan interface{})
@@ -379,7 +274,7 @@ func subscribeToVoter(cs *ConsensusState, addr []byte) chan interface{} {
 			v := <-voteCh0
 			vote := v.(types.EventDataVote)
 			// we only fire for our own votes
-			if bytes.Equal(addr, vote.Address) {
+			if bytes.Equal(addr, vote.Vote.ValidatorAddress) {
 				voteCh <- v
 			}
 		}
@@ -399,8 +294,8 @@ func readVotes(ch chan interface{}, reads int) chan struct{} {
 }
 
 func randGenesisState(numValidators int, randPower bool, minPower int64) (*sm.State, []*types.PrivValidator) {
-	db := dbm.NewMemDB()
 	genDoc, privValidators := randGenesisDoc(numValidators, randPower, minPower)
+	db := dbm.NewMemDB()
 	s0 := sm.MakeGenesisState(db, genDoc)
 	s0.Save()
 	return s0, privValidators
diff --git a/consensus/height_vote_set.go b/consensus/height_vote_set.go
index 5cc181b1..e7f4be3b 100644
--- a/consensus/height_vote_set.go
+++ b/consensus/height_vote_set.go
@@ -24,6 +24,8 @@ but which round is not known in advance, so when a peer
 provides a precommit for a round greater than mtx.round,
 we create a new entry in roundVoteSets but also remember the
 peer to prevent abuse.
+We let each peer provide us with up to 2 unexpected "catchup" rounds.
+One for their LastCommit round, and another for the official commit round.
 */
 type HeightVoteSet struct {
 	chainID string
@@ -33,7 +35,7 @@ type HeightVoteSet struct {
 	mtx               sync.Mutex
 	round             int                  // max tracked round
 	roundVoteSets     map[int]RoundVoteSet // keys: [0...round]
-	peerCatchupRounds map[string]int       // keys: peer.Key; values: round
+	peerCatchupRounds map[string][]int     // keys: peer.Key; values: at most 2 rounds
 }
 
 func NewHeightVoteSet(chainID string, height int, valSet *types.ValidatorSet) *HeightVoteSet {
@@ -51,7 +53,7 @@ func (hvs *HeightVoteSet) Reset(height int, valSet *types.ValidatorSet) {
 	hvs.height = height
 	hvs.valSet = valSet
 	hvs.roundVoteSets = make(map[int]RoundVoteSet)
-	hvs.peerCatchupRounds = make(map[string]int)
+	hvs.peerCatchupRounds = make(map[string][]int)
 
 	hvs.addRound(0)
 	hvs.round = 0
@@ -100,15 +102,18 @@ func (hvs *HeightVoteSet) addRound(round int) {
 
 // Duplicate votes return added=false, err=nil.
 // By convention, peerKey is "" if origin is self.
-func (hvs *HeightVoteSet) AddByIndex(valIndex int, vote *types.Vote, peerKey string) (added bool, address []byte, err error) {
+func (hvs *HeightVoteSet) AddVote(vote *types.Vote, peerKey string) (added bool, err error) {
 	hvs.mtx.Lock()
 	defer hvs.mtx.Unlock()
+	if !types.IsVoteTypeValid(vote.Type) {
+		return
+	}
 	voteSet := hvs.getVoteSet(vote.Round, vote.Type)
 	if voteSet == nil {
-		if _, ok := hvs.peerCatchupRounds[peerKey]; !ok {
+		if rndz := hvs.peerCatchupRounds[peerKey]; len(rndz) < 2 {
 			hvs.addRound(vote.Round)
 			voteSet = hvs.getVoteSet(vote.Round, vote.Type)
-			hvs.peerCatchupRounds[peerKey] = vote.Round
+			hvs.peerCatchupRounds[peerKey] = append(rndz, vote.Round)
 		} else {
 			// Peer has sent a vote that does not match our round,
 			// for more than one round.  Bad peer!
@@ -117,7 +122,7 @@ func (hvs *HeightVoteSet) AddByIndex(valIndex int, vote *types.Vote, peerKey str
 			return
 		}
 	}
-	added, address, err = voteSet.AddByIndex(valIndex, vote)
+	added, err = voteSet.AddVote(vote)
 	return
 }
 
@@ -133,17 +138,19 @@ func (hvs *HeightVoteSet) Precommits(round int) *types.VoteSet {
 	return hvs.getVoteSet(round, types.VoteTypePrecommit)
 }
 
-// Last round that has +2/3 prevotes for a particular block or nil.
+// Last round and blockID that has +2/3 prevotes for a particular block or nil.
 // Returns -1 if no such round exists.
-func (hvs *HeightVoteSet) POLRound() int {
+func (hvs *HeightVoteSet) POLInfo() (polRound int, polBlockID types.BlockID) {
 	hvs.mtx.Lock()
 	defer hvs.mtx.Unlock()
 	for r := hvs.round; r >= 0; r-- {
-		if hvs.getVoteSet(r, types.VoteTypePrevote).HasTwoThirdsMajority() {
-			return r
+		rvs := hvs.getVoteSet(r, types.VoteTypePrevote)
+		polBlockID, ok := rvs.TwoThirdsMajority()
+		if ok {
+			return r, polBlockID
 		}
 	}
-	return -1
+	return -1, types.BlockID{}
 }
 
 func (hvs *HeightVoteSet) getVoteSet(round int, type_ byte) *types.VoteSet {
@@ -194,3 +201,20 @@ func (hvs *HeightVoteSet) StringIndented(indent string) string {
 		indent, strings.Join(vsStrings, "\n"+indent+"  "),
 		indent)
 }
+
+// If a peer claims that it has 2/3 majority for given blockKey, call this.
+// NOTE: if there are too many peers, or too much peer churn,
+// this can cause memory issues.
+// TODO: implement ability to remove peers too
+func (hvs *HeightVoteSet) SetPeerMaj23(round int, type_ byte, peerID string, blockID types.BlockID) {
+	hvs.mtx.Lock()
+	defer hvs.mtx.Unlock()
+	if !types.IsVoteTypeValid(type_) {
+		return
+	}
+	voteSet := hvs.getVoteSet(round, type_)
+	if voteSet == nil {
+		return
+	}
+	voteSet.SetPeerMaj23(peerID, blockID)
+}
diff --git a/consensus/height_vote_set_test.go b/consensus/height_vote_set_test.go
index b5153259..3bede25c 100644
--- a/consensus/height_vote_set_test.go
+++ b/consensus/height_vote_set_test.go
@@ -17,31 +17,40 @@ func TestPeerCatchupRounds(t *testing.T) {
 
 	hvs := NewHeightVoteSet(config.GetString("chain_id"), 1, valSet)
 
-	vote999_0 := makeVoteHR(t, 1, 999, privVals[0])
-	added, _, err := hvs.AddByIndex(0, vote999_0, "peer1")
+	vote999_0 := makeVoteHR(t, 1, 999, privVals, 0)
+	added, err := hvs.AddVote(vote999_0, "peer1")
 	if !added || err != nil {
 		t.Error("Expected to successfully add vote from peer", added, err)
 	}
 
-	vote1000_0 := makeVoteHR(t, 1, 1000, privVals[0])
-	added, _, err = hvs.AddByIndex(0, vote1000_0, "peer1")
+	vote1000_0 := makeVoteHR(t, 1, 1000, privVals, 0)
+	added, err = hvs.AddVote(vote1000_0, "peer1")
+	if !added || err != nil {
+		t.Error("Expected to successfully add vote from peer", added, err)
+	}
+
+	vote1001_0 := makeVoteHR(t, 1, 1001, privVals, 0)
+	added, err = hvs.AddVote(vote1001_0, "peer1")
 	if added {
 		t.Error("Expected to *not* add vote from peer, too many catchup rounds.")
 	}
 
-	added, _, err = hvs.AddByIndex(0, vote1000_0, "peer2")
+	added, err = hvs.AddVote(vote1001_0, "peer2")
 	if !added || err != nil {
 		t.Error("Expected to successfully add vote from another peer")
 	}
 
 }
 
-func makeVoteHR(t *testing.T, height, round int, privVal *types.PrivValidator) *types.Vote {
+func makeVoteHR(t *testing.T, height, round int, privVals []*types.PrivValidator, valIndex int) *types.Vote {
+	privVal := privVals[valIndex]
 	vote := &types.Vote{
-		Height:    height,
-		Round:     round,
-		Type:      types.VoteTypePrecommit,
-		BlockHash: []byte("fakehash"),
+		ValidatorAddress: privVal.Address,
+		ValidatorIndex:   valIndex,
+		Height:           height,
+		Round:            round,
+		Type:             types.VoteTypePrecommit,
+		BlockID:          types.BlockID{[]byte("fakehash"), types.PartSetHeader{}},
 	}
 	chainID := config.GetString("chain_id")
 	err := privVal.SignVote(chainID, vote)
diff --git a/consensus/reactor.go b/consensus/reactor.go
index 4d5e5618..0ece82ce 100644
--- a/consensus/reactor.go
+++ b/consensus/reactor.go
@@ -11,18 +11,19 @@ import (
 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-p2p"
 	"github.com/tendermint/go-wire"
-	bc "github.com/tendermint/tendermint/blockchain"
 	sm "github.com/tendermint/tendermint/state"
 	"github.com/tendermint/tendermint/types"
 )
 
 const (
-	StateChannel = byte(0x20)
-	DataChannel  = byte(0x21)
-	VoteChannel  = byte(0x22)
+	StateChannel       = byte(0x20)
+	DataChannel        = byte(0x21)
+	VoteChannel        = byte(0x22)
+	VoteSetBitsChannel = byte(0x23)
 
-	peerGossipSleepDuration = 100 * time.Millisecond // Time to sleep if there's nothing to send.
-	maxConsensusMessageSize = 1048576                // 1MB; NOTE: keep in sync with types.PartSet sizes.
+	peerGossipSleepDuration     = 100 * time.Millisecond // Time to sleep if there's nothing to send.
+	peerQueryMaj23SleepDuration = 2 * time.Second        // Time to sleep after each VoteSetMaj23Message sent
+	maxConsensusMessageSize     = 1048576                // 1MB; NOTE: keep in sync with types.PartSet sizes.
 )
 
 //-----------------------------------------------------------------------------
@@ -30,17 +31,15 @@ const (
 type ConsensusReactor struct {
 	p2p.BaseReactor // BaseService + p2p.Switch
 
-	blockStore *bc.BlockStore
-	conS       *ConsensusState
-	fastSync   bool
-	evsw       types.EventSwitch
+	conS     *ConsensusState
+	fastSync bool
+	evsw     types.EventSwitch
 }
 
-func NewConsensusReactor(consensusState *ConsensusState, blockStore *bc.BlockStore, fastSync bool) *ConsensusReactor {
+func NewConsensusReactor(consensusState *ConsensusState, fastSync bool) *ConsensusReactor {
 	conR := &ConsensusReactor{
-		blockStore: blockStore,
-		conS:       consensusState,
-		fastSync:   fastSync,
+		conS:     consensusState,
+		fastSync: fastSync,
 	}
 	conR.BaseReactor = *p2p.NewBaseReactor(log, "ConsensusReactor", conR)
 	return conR
@@ -101,6 +100,12 @@ func (conR *ConsensusReactor) GetChannels() []*p2p.ChannelDescriptor {
 			SendQueueCapacity:  100,
 			RecvBufferCapacity: 100 * 100,
 		},
+		&p2p.ChannelDescriptor{
+			ID:                 VoteSetBitsChannel,
+			Priority:           1,
+			SendQueueCapacity:  2,
+			RecvBufferCapacity: 1024,
+		},
 	}
 }
 
@@ -114,9 +119,10 @@ func (conR *ConsensusReactor) AddPeer(peer *p2p.Peer) {
 	peerState := NewPeerState(peer)
 	peer.Data.Set(types.PeerStateKey, peerState)
 
-	// Begin gossip routines for this peer.
+	// Begin routines for this peer.
 	go conR.gossipDataRoutine(peer, peerState)
 	go conR.gossipVotesRoutine(peer, peerState)
+	go conR.queryMaj23Routine(peer, peerState)
 
 	// Send our state to peer.
 	// If we're fast_syncing, broadcast a RoundStepMessage later upon SwitchToConsensus().
@@ -166,6 +172,36 @@ func (conR *ConsensusReactor) Receive(chID byte, src *p2p.Peer, msgBytes []byte)
 			ps.ApplyCommitStepMessage(msg)
 		case *HasVoteMessage:
 			ps.ApplyHasVoteMessage(msg)
+		case *VoteSetMaj23Message:
+			cs := conR.conS
+			cs.mtx.Lock()
+			height, votes := cs.Height, cs.Votes
+			cs.mtx.Unlock()
+			if height != msg.Height {
+				return
+			}
+			// Peer claims to have a maj23 for some BlockID at H,R,S,
+			votes.SetPeerMaj23(msg.Round, msg.Type, ps.Peer.Key, msg.BlockID)
+			// Respond with a VoteSetBitsMessage showing which votes we have.
+			// (and consequently shows which we don't have)
+			var ourVotes *BitArray
+			switch msg.Type {
+			case types.VoteTypePrevote:
+				ourVotes = votes.Prevotes(msg.Round).BitArrayByBlockID(msg.BlockID)
+			case types.VoteTypePrecommit:
+				ourVotes = votes.Precommits(msg.Round).BitArrayByBlockID(msg.BlockID)
+			default:
+				log.Warn("Bad VoteSetBitsMessage field Type")
+				return
+			}
+			src.TrySend(VoteSetBitsChannel, struct{ ConsensusMessage }{&VoteSetBitsMessage{
+				Height:  msg.Height,
+				Round:   msg.Round,
+				Type:    msg.Type,
+				BlockID: msg.BlockID,
+				Votes:   ourVotes,
+			}})
+
 		default:
 			log.Warn(Fmt("Unknown message type %v", reflect.TypeOf(msg)))
 		}
@@ -201,7 +237,7 @@ func (conR *ConsensusReactor) Receive(chID byte, src *p2p.Peer, msgBytes []byte)
 			cs.mtx.Unlock()
 			ps.EnsureVoteBitArrays(height, valSize)
 			ps.EnsureVoteBitArrays(height-1, lastCommitSize)
-			ps.SetHasVote(msg.Vote, msg.ValidatorIndex)
+			ps.SetHasVote(msg.Vote)
 
 			conR.conS.peerMsgQueue <- msgInfo{msg, src.Key}
 
@@ -209,6 +245,39 @@ func (conR *ConsensusReactor) Receive(chID byte, src *p2p.Peer, msgBytes []byte)
 			// don't punish (leave room for soft upgrades)
 			log.Warn(Fmt("Unknown message type %v", reflect.TypeOf(msg)))
 		}
+
+	case VoteSetBitsChannel:
+		if conR.fastSync {
+			log.Warn("Ignoring message received during fastSync", "msg", msg)
+			return
+		}
+		switch msg := msg.(type) {
+		case *VoteSetBitsMessage:
+			cs := conR.conS
+			cs.mtx.Lock()
+			height, votes := cs.Height, cs.Votes
+			cs.mtx.Unlock()
+
+			if height == msg.Height {
+				var ourVotes *BitArray
+				switch msg.Type {
+				case types.VoteTypePrevote:
+					ourVotes = votes.Prevotes(msg.Round).BitArrayByBlockID(msg.BlockID)
+				case types.VoteTypePrecommit:
+					ourVotes = votes.Precommits(msg.Round).BitArrayByBlockID(msg.BlockID)
+				default:
+					log.Warn("Bad VoteSetBitsMessage field Type")
+					return
+				}
+				ps.ApplyVoteSetBitsMessage(msg, ourVotes)
+			} else {
+				ps.ApplyVoteSetBitsMessage(msg, nil)
+			}
+		default:
+			// don't punish (leave room for soft upgrades)
+			log.Warn(Fmt("Unknown message type %v", reflect.TypeOf(msg)))
+		}
+
 	default:
 		log.Warn(Fmt("Unknown chId %X", chID))
 	}
@@ -219,7 +288,7 @@ func (conR *ConsensusReactor) Receive(chID byte, src *p2p.Peer, msgBytes []byte)
 }
 
 // Sets our private validator account for signing votes.
-func (conR *ConsensusReactor) SetPrivValidator(priv *types.PrivValidator) {
+func (conR *ConsensusReactor) SetPrivValidator(priv PrivValidator) {
 	conR.conS.SetPrivValidator(priv)
 }
 
@@ -242,7 +311,7 @@ func (conR *ConsensusReactor) registerEventCallbacks() {
 
 	types.AddListenerForEvent(conR.evsw, "conR", types.EventStringVote(), func(data types.TMEventData) {
 		edv := data.(types.EventDataVote)
-		conR.broadcastHasVoteMessage(edv.Vote, edv.Index)
+		conR.broadcastHasVoteMessage(edv.Vote)
 	})
 }
 
@@ -258,12 +327,12 @@ func (conR *ConsensusReactor) broadcastNewRoundStep(rs *RoundState) {
 }
 
 // Broadcasts HasVoteMessage to peers that care.
-func (conR *ConsensusReactor) broadcastHasVoteMessage(vote *types.Vote, index int) {
+func (conR *ConsensusReactor) broadcastHasVoteMessage(vote *types.Vote) {
 	msg := &HasVoteMessage{
 		Height: vote.Height,
 		Round:  vote.Round,
 		Type:   vote.Type,
-		Index:  index,
+		Index:  vote.ValidatorIndex,
 	}
 	conR.Switch.Broadcast(StateChannel, struct{ ConsensusMessage }{msg})
 	/*
@@ -346,15 +415,19 @@ OUTER_LOOP:
 			//log.Info("Data catchup", "height", rs.Height, "peerHeight", prs.Height, "peerProposalBlockParts", prs.ProposalBlockParts)
 			if index, ok := prs.ProposalBlockParts.Not().PickRandom(); ok {
 				// Ensure that the peer's PartSetHeader is correct
-				blockMeta := conR.blockStore.LoadBlockMeta(prs.Height)
-				if !blockMeta.PartsHeader.Equals(prs.ProposalBlockPartsHeader) {
+				blockMeta := conR.conS.blockStore.LoadBlockMeta(prs.Height)
+				if blockMeta == nil {
+					log.Warn("Failed to load block meta", "peer height", prs.Height, "our height", rs.Height, "blockstore height", conR.conS.blockStore.Height(), "pv", conR.conS.privValidator)
+					time.Sleep(peerGossipSleepDuration)
+					continue OUTER_LOOP
+				} else if !blockMeta.PartsHeader.Equals(prs.ProposalBlockPartsHeader) {
 					log.Info("Peer ProposalBlockPartsHeader mismatch, sleeping",
 						"peerHeight", prs.Height, "blockPartsHeader", blockMeta.PartsHeader, "peerBlockPartsHeader", prs.ProposalBlockPartsHeader)
 					time.Sleep(peerGossipSleepDuration)
 					continue OUTER_LOOP
 				}
 				// Load the part
-				part := conR.blockStore.LoadBlockPart(prs.Height, index)
+				part := conR.conS.blockStore.LoadBlockPart(prs.Height, index)
 				if part == nil {
 					log.Warn("Could not load part", "index", index,
 						"peerHeight", prs.Height, "blockPartsHeader", blockMeta.PartsHeader, "peerBlockPartsHeader", prs.ProposalBlockPartsHeader)
@@ -391,13 +464,13 @@ OUTER_LOOP:
 
 		// Send Proposal && ProposalPOL BitArray?
 		if rs.Proposal != nil && !prs.Proposal {
-			// Proposal
+			// Proposal: share the proposal metadata with peer.
 			{
 				msg := &ProposalMessage{Proposal: rs.Proposal}
 				peer.Send(DataChannel, struct{ ConsensusMessage }{msg})
 				ps.SetHasProposal(rs.Proposal)
 			}
-			// ProposalPOL.
+			// ProposalPOL: lets peer know which POL votes we have so far.
 			// Peer must receive ProposalMessage first.
 			// rs.Proposal was validated, so rs.Proposal.POLRound <= rs.Round,
 			// so we definitely have rs.Votes.Prevotes(rs.Proposal.POLRound).
@@ -492,8 +565,8 @@ OUTER_LOOP:
 		if prs.Height != 0 && rs.Height >= prs.Height+2 {
 			// Load the block commit for prs.Height,
 			// which contains precommit signatures for prs.Height.
-			commit := conR.blockStore.LoadBlockCommit(prs.Height)
-			log.Debug("Loaded BlockCommit for catch-up", "height", prs.Height, "commit", commit)
+			commit := conR.conS.blockStore.LoadBlockCommit(prs.Height)
+			log.Info("Loaded BlockCommit for catch-up", "height", prs.Height, "commit", commit)
 			if ps.PickSendVote(commit) {
 				log.Debug("Picked Catchup commit to send")
 				continue OUTER_LOOP
@@ -516,6 +589,112 @@ OUTER_LOOP:
 	}
 }
 
+func (conR *ConsensusReactor) queryMaj23Routine(peer *p2p.Peer, ps *PeerState) {
+	log := log.New("peer", peer)
+
+OUTER_LOOP:
+	for {
+		// Manage disconnects from self or peer.
+		if !peer.IsRunning() || !conR.IsRunning() {
+			log.Notice(Fmt("Stopping queryMaj23Routine for %v.", peer))
+			return
+		}
+
+		// Maybe send Height/Round/Prevotes
+		{
+			rs := conR.conS.GetRoundState()
+			prs := ps.GetRoundState()
+			if rs.Height == prs.Height {
+				if maj23, ok := rs.Votes.Prevotes(prs.Round).TwoThirdsMajority(); ok {
+					peer.TrySend(StateChannel, struct{ ConsensusMessage }{&VoteSetMaj23Message{
+						Height:  prs.Height,
+						Round:   prs.Round,
+						Type:    types.VoteTypePrevote,
+						BlockID: maj23,
+					}})
+					time.Sleep(peerQueryMaj23SleepDuration)
+				}
+			}
+		}
+
+		// Maybe send Height/Round/Precommits
+		{
+			rs := conR.conS.GetRoundState()
+			prs := ps.GetRoundState()
+			if rs.Height == prs.Height {
+				if maj23, ok := rs.Votes.Precommits(prs.Round).TwoThirdsMajority(); ok {
+					peer.TrySend(StateChannel, struct{ ConsensusMessage }{&VoteSetMaj23Message{
+						Height:  prs.Height,
+						Round:   prs.Round,
+						Type:    types.VoteTypePrecommit,
+						BlockID: maj23,
+					}})
+					time.Sleep(peerQueryMaj23SleepDuration)
+				}
+			}
+		}
+
+		// Maybe send Height/Round/ProposalPOL
+		{
+			rs := conR.conS.GetRoundState()
+			prs := ps.GetRoundState()
+			if rs.Height == prs.Height && prs.ProposalPOLRound >= 0 {
+				if maj23, ok := rs.Votes.Prevotes(prs.ProposalPOLRound).TwoThirdsMajority(); ok {
+					peer.TrySend(StateChannel, struct{ ConsensusMessage }{&VoteSetMaj23Message{
+						Height:  prs.Height,
+						Round:   prs.ProposalPOLRound,
+						Type:    types.VoteTypePrevote,
+						BlockID: maj23,
+					}})
+					time.Sleep(peerQueryMaj23SleepDuration)
+				}
+			}
+		}
+
+		// Little point sending LastCommitRound/LastCommit,
+		// These are fleeting and non-blocking.
+
+		// Maybe send Height/CatchupCommitRound/CatchupCommit.
+		{
+			prs := ps.GetRoundState()
+			if prs.CatchupCommitRound != -1 && 0 < prs.Height && prs.Height <= conR.conS.blockStore.Height() {
+				var commit *types.Commit
+				if prs.Height == conR.conS.blockStore.Height() {
+					commit = conR.conS.blockStore.LoadSeenCommit(prs.Height)
+				} else {
+					commit = conR.conS.blockStore.LoadBlockCommit(prs.Height)
+				}
+				peer.TrySend(StateChannel, struct{ ConsensusMessage }{&VoteSetMaj23Message{
+					Height:  prs.Height,
+					Round:   commit.Round(),
+					Type:    types.VoteTypePrecommit,
+					BlockID: commit.BlockID,
+				}})
+				time.Sleep(peerQueryMaj23SleepDuration)
+			}
+		}
+
+		time.Sleep(peerQueryMaj23SleepDuration)
+
+		continue OUTER_LOOP
+	}
+}
+
+func (conR *ConsensusReactor) String() string {
+	return conR.StringIndented("")
+}
+
+func (conR *ConsensusReactor) StringIndented(indent string) string {
+	s := "ConsensusReactor{\n"
+	s += indent + "  " + conR.conS.StringIndented(indent+"  ") + "\n"
+	for _, peer := range conR.Switch.Peers().List() {
+		ps := peer.Data.Get(types.PeerStateKey).(*PeerState)
+		s += indent + "  " + ps.StringIndented(indent+"  ") + "\n"
+	}
+	s += indent + "}"
+	return s
+}
+
 //-----------------------------------------------------------------------------
 
 // Read only when returned by PeerState.GetRoundState().
@@ -537,6 +716,30 @@ type PeerRoundState struct {
 	CatchupCommit            *BitArray           // All commit precommits peer has for this height & CatchupCommitRound
 }
 
+func (prs PeerRoundState) String() string {
+	return prs.StringIndented("")
+}
+
+func (prs PeerRoundState) StringIndented(indent string) string {
+	return fmt.Sprintf(`PeerRoundState{
+%s  %v/%v/%v @%v
+%s  Proposal %v -> %v
+%s  POL      %v (round %v)
+%s  Prevotes   %v
+%s  Precommits %v
+%s  LastCommit %v (round %v)
+%s  Catchup    %v (round %v)
+%s}`,
+		indent, prs.Height, prs.Round, prs.Step, prs.StartTime,
+		indent, prs.ProposalBlockPartsHeader, prs.ProposalBlockParts,
+		indent, prs.ProposalPOL, prs.ProposalPOLRound,
+		indent, prs.Prevotes,
+		indent, prs.Precommits,
+		indent, prs.LastCommit, prs.LastCommitRound,
+		indent, prs.CatchupCommit, prs.CatchupCommitRound,
+		indent)
+}
+
 //-----------------------------------------------------------------------------
 
 var (
@@ -613,8 +816,8 @@ func (ps *PeerState) SetHasProposalBlockPart(height int, round int, index int) {
 // Convenience function to send vote to peer.
 // Returns true if vote was sent.
 func (ps *PeerState) PickSendVote(votes types.VoteSetReader) (ok bool) {
-	if index, vote, ok := ps.PickVoteToSend(votes); ok {
-		msg := &VoteMessage{index, vote}
+	if vote, ok := ps.PickVoteToSend(votes); ok {
+		msg := &VoteMessage{vote}
 		ps.Peer.Send(VoteChannel, struct{ ConsensusMessage }{msg})
 		return true
 	}
@@ -622,12 +825,12 @@ func (ps *PeerState) PickSendVote(votes types.VoteSetReader) (ok bool) {
 }
 
 // votes: Must be the correct Size() for the Height().
-func (ps *PeerState) PickVoteToSend(votes types.VoteSetReader) (index int, vote *types.Vote, ok bool) {
+func (ps *PeerState) PickVoteToSend(votes types.VoteSetReader) (vote *types.Vote, ok bool) {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 
 	if votes.Size() == 0 {
-		return 0, nil, false
+		return nil, false
 	}
 
 	height, round, type_, size := votes.Height(), votes.Round(), votes.Type(), votes.Size()
@@ -640,16 +843,20 @@ func (ps *PeerState) PickVoteToSend(votes types.VoteSetReader) (index int, vote
 
 	psVotes := ps.getVoteBitArray(height, round, type_)
 	if psVotes == nil {
-		return 0, nil, false // Not something worth sending
+		return nil, false // Not something worth sending
 	}
 	if index, ok := votes.BitArray().Sub(psVotes).PickRandom(); ok {
 		ps.setHasVote(height, round, type_, index)
-		return index, votes.GetByIndex(index), true
+		return votes.GetByIndex(index), true
 	}
-	return 0, nil, false
+	return nil, false
 }
 
 func (ps *PeerState) getVoteBitArray(height, round int, type_ byte) *BitArray {
+	if !types.IsVoteTypeValid(type_) {
+		PanicSanity("Invalid vote type")
+	}
+
 	if ps.Height == height {
 		if ps.Round == round {
 			switch type_ {
@@ -657,8 +864,6 @@ func (ps *PeerState) getVoteBitArray(height, round int, type_ byte) *BitArray {
 				return ps.Prevotes
 			case types.VoteTypePrecommit:
 				return ps.Precommits
-			default:
-				PanicSanity(Fmt("Unexpected vote type %X", type_))
 			}
 		}
 		if ps.CatchupCommitRound == round {
@@ -667,8 +872,14 @@ func (ps *PeerState) getVoteBitArray(height, round int, type_ byte) *BitArray {
 				return nil
 			case types.VoteTypePrecommit:
 				return ps.CatchupCommit
-			default:
-				PanicSanity(Fmt("Unexpected vote type %X", type_))
+			}
+		}
+		if ps.ProposalPOLRound == round {
+			switch type_ {
+			case types.VoteTypePrevote:
+				return ps.ProposalPOL
+			case types.VoteTypePrecommit:
+				return nil
 			}
 		}
 		return nil
@@ -680,8 +891,6 @@ func (ps *PeerState) getVoteBitArray(height, round int, type_ byte) *BitArray {
 				return nil
 			case types.VoteTypePrecommit:
 				return ps.LastCommit
-			default:
-				PanicSanity(Fmt("Unexpected vote type %X", type_))
 			}
 		}
 		return nil
@@ -741,56 +950,19 @@ func (ps *PeerState) ensureVoteBitArrays(height int, numValidators int) {
 	}
 }
 
-func (ps *PeerState) SetHasVote(vote *types.Vote, index int) {
+func (ps *PeerState) SetHasVote(vote *types.Vote) {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 
-	ps.setHasVote(vote.Height, vote.Round, vote.Type, index)
+	ps.setHasVote(vote.Height, vote.Round, vote.Type, vote.ValidatorIndex)
 }
 
 func (ps *PeerState) setHasVote(height int, round int, type_ byte, index int) {
 	log := log.New("peer", ps.Peer, "peerRound", ps.Round, "height", height, "round", round)
-	if type_ != types.VoteTypePrevote && type_ != types.VoteTypePrecommit {
-		PanicSanity("Invalid vote type")
-	}
+	log.Info("setHasVote(LastCommit)", "lastCommit", ps.LastCommit, "index", index)
 
-	if ps.Height == height {
-		if ps.Round == round {
-			switch type_ {
-			case types.VoteTypePrevote:
-				ps.Prevotes.SetIndex(index, true)
-				log.Debug("SetHasVote(round-match)", "prevotes", ps.Prevotes, "index", index)
-			case types.VoteTypePrecommit:
-				ps.Precommits.SetIndex(index, true)
-				log.Debug("SetHasVote(round-match)", "precommits", ps.Precommits, "index", index)
-			}
-		} else if ps.CatchupCommitRound == round {
-			switch type_ {
-			case types.VoteTypePrevote:
-			case types.VoteTypePrecommit:
-				ps.CatchupCommit.SetIndex(index, true)
-				log.Debug("SetHasVote(CatchupCommit)", "precommits", ps.Precommits, "index", index)
-			}
-		} else if ps.ProposalPOLRound == round {
-			switch type_ {
-			case types.VoteTypePrevote:
-				ps.ProposalPOL.SetIndex(index, true)
-				log.Debug("SetHasVote(ProposalPOL)", "prevotes", ps.Prevotes, "index", index)
-			case types.VoteTypePrecommit:
-			}
-		}
-	} else if ps.Height == height+1 {
-		if ps.LastCommitRound == round {
-			switch type_ {
-			case types.VoteTypePrevote:
-			case types.VoteTypePrecommit:
-				ps.LastCommit.SetIndex(index, true)
-				log.Debug("setHasVote(LastCommit)", "lastCommit", ps.LastCommit, "index", index)
-			}
-		}
-	} else {
-		// Does not apply.
-	}
+	// NOTE: some may be nil BitArrays -> no side effects.
+	ps.getVoteBitArray(height, round, type_).SetIndex(index, true)
 }
 
 func (ps *PeerState) ApplyNewRoundStepMessage(msg *NewRoundStepMessage) {
@@ -858,17 +1030,6 @@ func (ps *PeerState) ApplyCommitStepMessage(msg *CommitStepMessage) {
 	ps.ProposalBlockParts = msg.BlockParts
 }
 
-func (ps *PeerState) ApplyHasVoteMessage(msg *HasVoteMessage) {
-	ps.mtx.Lock()
-	defer ps.mtx.Unlock()
-
-	if ps.Height != msg.Height {
-		return
-	}
-
-	ps.setHasVote(msg.Height, msg.Round, msg.Type, msg.Index)
-}
-
 func (ps *PeerState) ApplyProposalPOLMessage(msg *ProposalPOLMessage) {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
@@ -885,6 +1046,52 @@ func (ps *PeerState) ApplyProposalPOLMessage(msg *ProposalPOLMessage) {
 	ps.ProposalPOL = msg.ProposalPOL
 }
 
+func (ps *PeerState) ApplyHasVoteMessage(msg *HasVoteMessage) {
+	ps.mtx.Lock()
+	defer ps.mtx.Unlock()
+
+	if ps.Height != msg.Height {
+		return
+	}
+
+	ps.setHasVote(msg.Height, msg.Round, msg.Type, msg.Index)
+}
+
+// The peer has responded with a bitarray of votes that it has
+// of the corresponding BlockID.
+// ourVotes: BitArray of votes we have for msg.BlockID
+// NOTE: if ourVotes is nil (e.g. msg.Height < rs.Height),
+// we conservatively overwrite ps's votes w/ msg.Votes.
+func (ps *PeerState) ApplyVoteSetBitsMessage(msg *VoteSetBitsMessage, ourVotes *BitArray) {
+	ps.mtx.Lock()
+	defer ps.mtx.Unlock()
+
+	votes := ps.getVoteBitArray(msg.Height, msg.Round, msg.Type)
+	if votes != nil {
+		if ourVotes == nil {
+			votes.Update(msg.Votes)
+		} else {
+			otherVotes := votes.Sub(ourVotes)
+			hasVotes := otherVotes.Or(msg.Votes)
+			votes.Update(hasVotes)
+		}
+	}
+}
+
+func (ps *PeerState) String() string {
+	return ps.StringIndented("")
+}
+
+func (ps *PeerState) StringIndented(indent string) string {
+	return fmt.Sprintf(`PeerState{
+%s  Key %v
+%s  PRS %v
+%s}`,
+		indent, ps.Peer.Key,
+		indent, ps.PeerRoundState.StringIndented(indent+"  "),
+		indent)
+}
+
 //-----------------------------------------------------------------------------
 // Messages
 
@@ -896,6 +1103,8 @@ const (
 	msgTypeBlockPart    = byte(0x13) // both block & POL
 	msgTypeVote         = byte(0x14)
 	msgTypeHasVote      = byte(0x15)
+	msgTypeVoteSetMaj23 = byte(0x16)
+	msgTypeVoteSetBits  = byte(0x17)
 )
 
 type ConsensusMessage interface{}
@@ -909,6 +1118,8 @@ var _ = wire.RegisterInterface(
 	wire.ConcreteType{&BlockPartMessage{}, msgTypeBlockPart},
 	wire.ConcreteType{&VoteMessage{}, msgTypeVote},
 	wire.ConcreteType{&HasVoteMessage{}, msgTypeHasVote},
+	wire.ConcreteType{&VoteSetMaj23Message{}, msgTypeVoteSetMaj23},
+	wire.ConcreteType{&VoteSetBitsMessage{}, msgTypeVoteSetBits},
 )
 
 // TODO: check for unnecessary extra bytes at the end.
@@ -985,12 +1196,11 @@ func (m *BlockPartMessage) String() string {
 //-------------------------------------
 
 type VoteMessage struct {
-	ValidatorIndex int
-	Vote           *types.Vote
+	Vote *types.Vote
 }
 
 func (m *VoteMessage) String() string {
-	return fmt.Sprintf("[Vote VI:%v V:%v VI:%v]", m.ValidatorIndex, m.Vote, m.ValidatorIndex)
+	return fmt.Sprintf("[Vote %v]", m.Vote)
 }
 
 //-------------------------------------
@@ -1005,3 +1215,30 @@ type HasVoteMessage struct {
 func (m *HasVoteMessage) String() string {
 	return fmt.Sprintf("[HasVote VI:%v V:{%v/%02d/%v} VI:%v]", m.Index, m.Height, m.Round, m.Type, m.Index)
 }
+
+//-------------------------------------
+
+type VoteSetMaj23Message struct {
+	Height  int
+	Round   int
+	Type    byte
+	BlockID types.BlockID
+}
+
+func (m *VoteSetMaj23Message) String() string {
+	return fmt.Sprintf("[VSM23 %v/%02d/%v %v]", m.Height, m.Round, m.Type, m.BlockID)
+}
+
+//-------------------------------------
+
+type VoteSetBitsMessage struct {
+	Height  int
+	Round   int
+	Type    byte
+	BlockID types.BlockID
+	Votes   *BitArray
+}
+
+func (m *VoteSetBitsMessage) String() string {
+	return fmt.Sprintf("[VSB %v/%02d/%v %v %v]", m.Height, m.Round, m.Type, m.BlockID, m.Votes)
+}
diff --git a/consensus/reactor_test.go b/consensus/reactor_test.go
new file mode 100644
index 00000000..6b76d2aa
--- /dev/null
+++ b/consensus/reactor_test.go
@@ -0,0 +1,351 @@
+package consensus
+
+import (
+	"bytes"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/tendermint/tendermint/config/tendermint_test"
+
+	. "github.com/tendermint/go-common"
+	cfg "github.com/tendermint/go-config"
+	"github.com/tendermint/go-crypto"
+	"github.com/tendermint/go-events"
+	"github.com/tendermint/go-logger"
+	"github.com/tendermint/go-p2p"
+	"github.com/tendermint/tendermint/types"
+)
+
+func init() {
+	config = tendermint_test.ResetConfig("consensus_reactor_test")
+}
+
+func resetConfigTimeouts() {
+	logger.SetLogLevel("notice")
+	//config.Set("log_level", "notice")
+	config.Set("timeout_propose", 2000)
+	//	config.Set("timeout_propose_delta", 500)
+	//	config.Set("timeout_prevote", 1000)
+	//	config.Set("timeout_prevote_delta", 500)
+	//	config.Set("timeout_precommit", 1000)
+	//	config.Set("timeout_precommit_delta", 500)
+	//	config.Set("timeout_commit", 1000)
+}
+
+func TestReactor(t *testing.T) {
+	resetConfigTimeouts()
+	N := 4
+	css := randConsensusNet(N)
+	reactors := make([]*ConsensusReactor, N)
+	eventChans := make([]chan interface{}, N)
+	for i := 0; i < N; i++ {
+		reactors[i] = NewConsensusReactor(css[i], false)
+		reactors[i].SetPrivValidator(css[i].privValidator)
+
+		eventSwitch := events.NewEventSwitch()
+		_, err := eventSwitch.Start()
+		if err != nil {
+			t.Fatalf("Failed to start switch: %v", err)
+		}
+
+		reactors[i].SetEventSwitch(eventSwitch)
+		eventChans[i] = subscribeToEvent(eventSwitch, "tester", types.EventStringNewBlock(), 1)
+	}
+	p2p.MakeConnectedSwitches(N, func(i int, s *p2p.Switch) *p2p.Switch {
+		s.AddReactor("CONSENSUS", reactors[i])
+		return s
+	}, p2p.Connect2Switches)
+
+	// wait till everyone makes the first new block
+	wg := new(sync.WaitGroup)
+	wg.Add(N)
+	for i := 0; i < N; i++ {
+		go func(j int) {
+			<-eventChans[j]
+			wg.Done()
+		}(i)
+	}
+
+	// Make wait into a channel
+	done := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+
+	tick := time.NewTicker(time.Second * 3)
+	select {
+	case <-done:
+	case <-tick.C:
+		t.Fatalf("Timed out waiting for all validators to commit first block")
+	}
+}
+
+// 4 validators. 1 is byzantine. The other three are partitioned into A (1 val) and B (2 vals).
+// byzantine validator sends conflicting proposals into A and B,
+// and prevotes/precommits on both of them.
+// B sees a commit, A doesn't.
+// Byzantine validator refuses to prevote.
+// Heal partition and ensure A sees the commit
+func TestByzantine(t *testing.T) {
+	resetConfigTimeouts()
+	N := 4
+	css := randConsensusNet(N)
+
+	switches := make([]*p2p.Switch, N)
+	for i := 0; i < N; i++ {
+		switches[i] = p2p.NewSwitch(cfg.NewMapConfig(nil))
+	}
+
+	reactors := make([]p2p.Reactor, N)
+	eventChans := make([]chan interface{}, N)
+	for i := 0; i < N; i++ {
+		var privVal PrivValidator
+		privVal = css[i].privValidator
+		if i == 0 {
+			privVal = NewByzantinePrivValidator(privVal.(*types.PrivValidator))
+			// make byzantine
+			css[i].decideProposal = func(j int) func(int, int) {
+				return func(height, round int) {
+					byzantineDecideProposalFunc(height, round, css[j], switches[j])
+				}
+			}(i)
+			css[i].doPrevote = func(height, round int) {}
+		}
+
+		eventSwitch := events.NewEventSwitch()
+		_, err := eventSwitch.Start()
+		if err != nil {
+			t.Fatalf("Failed to start switch: %v", err)
+		}
+		eventChans[i] = subscribeToEvent(eventSwitch, "tester", types.EventStringNewBlock(), 1)
+
+		conR := NewConsensusReactor(css[i], false)
+		conR.SetPrivValidator(privVal)
+		conR.SetEventSwitch(eventSwitch)
+
+		var conRI p2p.Reactor
+		conRI = conR
+		if i == 0 {
+			conRI = NewByzantineReactor(conR)
+		}
+		reactors[i] = conRI
+	}
+
+	p2p.MakeConnectedSwitches(N, func(i int, s *p2p.Switch) *p2p.Switch {
+		// ignore new switch s, we already made ours
+		switches[i].AddReactor("CONSENSUS", reactors[i])
+		return switches[i]
+	}, func(sws []*p2p.Switch, i, j int) {
+		// the network starts partitioned with globally active adversary
+		if i != 0 {
+			return
+		}
+		p2p.Connect2Switches(sws, i, j)
+	})
+
+	// byz proposer sends one block to peers[0]
+	// and the other block to peers[1] and peers[2].
+	// note peers and switches order don't match.
+	peers := switches[0].Peers().List()
+	ind0 := getSwitchIndex(switches, peers[0])
+	ind1 := getSwitchIndex(switches, peers[1])
+	ind2 := getSwitchIndex(switches, peers[2])
+
+	// connect the 2 peers in the larger partition
+	p2p.Connect2Switches(switches, ind1, ind2)
+
+	// wait for someone in the big partition to make a block
+
+	select {
+	case <-eventChans[ind2]:
+	}
+
+	log.Notice("A block has been committed. Healing partition")
+
+	// connect the partitions
+	p2p.Connect2Switches(switches, ind0, ind1)
+	p2p.Connect2Switches(switches, ind0, ind2)
+
+	// wait till everyone makes the first new block
+	// (one of them already has)
+	wg := new(sync.WaitGroup)
+	wg.Add(2)
+	for i := 1; i < N-1; i++ {
+		go func(j int) {
+			<-eventChans[j]
+			wg.Done()
+		}(i)
+	}
+
+	done := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+
+	tick := time.NewTicker(time.Second * 10)
+	select {
+	case <-done:
+	case <-tick.C:
+		for i, reactor := range reactors {
+			t.Log(Fmt("Consensus Reactor %v", i))
+			t.Log(Fmt("%v", reactor))
+		}
+		t.Fatalf("Timed out waiting for all validators to commit first block")
+	}
+}
+
+func getSwitchIndex(switches []*p2p.Switch, peer *p2p.Peer) int {
+	for i, s := range switches {
+		if bytes.Equal(peer.NodeInfo.PubKey.Address(), s.NodeInfo().PubKey.Address()) {
+			return i
+		}
+	}
+	panic("didnt find peer in switches")
+	return -1
+}
+
+//-------------------------------
+// byzantine consensus functions
+
+func byzantineDecideProposalFunc(height, round int, cs *ConsensusState, sw *p2p.Switch) {
+	// byzantine user should create two proposals and try to split the vote.
+	// Avoid sending on internalMsgQueue and running consensus state.
+
+	// Create a new proposal block from state/txs from the mempool.
+	block1, blockParts1 := cs.createProposalBlock()
+	polRound, polBlockID := cs.Votes.POLInfo()
+	proposal1 := types.NewProposal(height, round, blockParts1.Header(), polRound, polBlockID)
+	cs.privValidator.SignProposal(cs.state.ChainID, proposal1) // byzantine doesnt err
+
+	// Create a new proposal block from state/txs from the mempool.
+	block2, blockParts2 := cs.createProposalBlock()
+	polRound, polBlockID = cs.Votes.POLInfo()
+	proposal2 := types.NewProposal(height, round, blockParts2.Header(), polRound, polBlockID)
+	cs.privValidator.SignProposal(cs.state.ChainID, proposal2) // byzantine doesnt err
+
+	block1Hash := block1.Hash()
+	block2Hash := block2.Hash()
+
+	// broadcast conflicting proposals/block parts to peers
+	peers := sw.Peers().List()
+	log.Notice("Byzantine: broadcasting conflicting proposals", "peers", len(peers))
+	for i, peer := range peers {
+		if i < len(peers)/2 {
+			go sendProposalAndParts(height, round, cs, peer, proposal1, block1Hash, blockParts1)
+		} else {
+			go sendProposalAndParts(height, round, cs, peer, proposal2, block2Hash, blockParts2)
+		}
+	}
+}
+
+func sendProposalAndParts(height, round int, cs *ConsensusState, peer *p2p.Peer, proposal *types.Proposal, blockHash []byte, parts *types.PartSet) {
+	// proposal
+	msg := &ProposalMessage{Proposal: proposal}
+	peer.Send(DataChannel, struct{ ConsensusMessage }{msg})
+
+	// parts
+	for i := 0; i < parts.Total(); i++ {
+		part := parts.GetPart(i)
+		msg := &BlockPartMessage{
+			Height: height, // This tells peer that this part applies to us.
+			Round:  round,  // This tells peer that this part applies to us.
+			Part:   part,
+		}
+		peer.Send(DataChannel, struct{ ConsensusMessage }{msg})
+	}
+
+	// votes
+	cs.mtx.Lock()
+	prevote, _ := cs.signVote(types.VoteTypePrevote, blockHash, parts.Header())
+	precommit, _ := cs.signVote(types.VoteTypePrecommit, blockHash, parts.Header())
+	cs.mtx.Unlock()
+
+	peer.Send(VoteChannel, struct{ ConsensusMessage }{&VoteMessage{prevote}})
+	peer.Send(VoteChannel, struct{ ConsensusMessage }{&VoteMessage{precommit}})
+}
+
+//----------------------------------------
+// byzantine consensus reactor
+
+type ByzantineReactor struct {
+	Service
+	reactor *ConsensusReactor
+}
+
+func NewByzantineReactor(conR *ConsensusReactor) *ByzantineReactor {
+	return &ByzantineReactor{
+		Service: conR,
+		reactor: conR,
+	}
+}
+
+func (br *ByzantineReactor) SetSwitch(s *p2p.Switch)               { br.reactor.SetSwitch(s) }
+func (br *ByzantineReactor) GetChannels() []*p2p.ChannelDescriptor { return br.reactor.GetChannels() }
+func (br *ByzantineReactor) AddPeer(peer *p2p.Peer) {
+	if !br.reactor.IsRunning() {
+		return
+	}
+
+	// Create peerState for peer
+	peerState := NewPeerState(peer)
+	peer.Data.Set(types.PeerStateKey, peerState)
+
+	// Send our state to peer.
+	// If we're fast_syncing, broadcast a RoundStepMessage later upon SwitchToConsensus().
+	if !br.reactor.fastSync {
+		br.reactor.sendNewRoundStepMessage(peer)
+	}
+}
+func (br *ByzantineReactor) RemovePeer(peer *p2p.Peer, reason interface{}) {
+	br.reactor.RemovePeer(peer, reason)
+}
+func (br *ByzantineReactor) Receive(chID byte, peer *p2p.Peer, msgBytes []byte) {
+	br.reactor.Receive(chID, peer, msgBytes)
+}
+
+//----------------------------------------
+// byzantine privValidator
+
+type ByzantinePrivValidator struct {
+	Address      []byte `json:"address"`
+	types.Signer `json:"-"`
+
+	mtx sync.Mutex
+}
+
+// Return a priv validator that will sign anything
+func NewByzantinePrivValidator(pv *types.PrivValidator) *ByzantinePrivValidator {
+	return &ByzantinePrivValidator{
+		Address: pv.Address,
+		Signer:  pv.Signer,
+	}
+}
+
+func (privVal *ByzantinePrivValidator) GetAddress() []byte {
+	return privVal.Address
+}
+
+func (privVal *ByzantinePrivValidator) SignVote(chainID string, vote *types.Vote) error {
+	privVal.mtx.Lock()
+	defer privVal.mtx.Unlock()
+
+	// Sign
+	vote.Signature = privVal.Sign(types.SignBytes(chainID, vote)).(crypto.SignatureEd25519)
+	return nil
+}
+
+func (privVal *ByzantinePrivValidator) SignProposal(chainID string, proposal *types.Proposal) error {
+	privVal.mtx.Lock()
+	defer privVal.mtx.Unlock()
+
+	// Sign
+	proposal.Signature = privVal.Sign(types.SignBytes(chainID, proposal)).(crypto.SignatureEd25519)
+	return nil
+}
+
+func (privVal *ByzantinePrivValidator) String() string {
+	return Fmt("PrivValidator{%X}", privVal.Address)
+}
diff --git a/consensus/replay.go b/consensus/replay.go
index 54e3c134..b9d02c17 100644
--- a/consensus/replay.go
+++ b/consensus/replay.go
@@ -68,7 +68,7 @@ func (cs *ConsensusState) readReplayMessage(msgBytes []byte, newStepCh chan inte
 		case *VoteMessage:
 			v := msg.Vote
 			log.Notice("Replay: Vote", "height", v.Height, "round", v.Round, "type", v.Type,
-				"hash", v.BlockHash, "header", v.BlockPartsHeader, "peer", peerKey)
+				"blockID", v.BlockID, "peer", peerKey)
 		}
 
 		cs.handleMsg(m, cs.RoundState)
diff --git a/consensus/replay_test.go b/consensus/replay_test.go
index b3626c86..2f251de2 100644
--- a/consensus/replay_test.go
+++ b/consensus/replay_test.go
@@ -21,9 +21,9 @@ var baseStepChanges = []int{3, 6, 8}
 
 // test recovery from each line in each testCase
 var testCases = []*testCase{
-	newTestCase("empty_block", baseStepChanges),  // empty block (has 1 block part)
-	newTestCase("small_block1", baseStepChanges), // small block with txs in 1 block part
-	newTestCase("small_block2", []int{3, 8, 10}), // small block with txs across 3 smaller block parts
+	newTestCase("empty_block", baseStepChanges),   // empty block (has 1 block part)
+	newTestCase("small_block1", baseStepChanges),  // small block with txs in 1 block part
+	newTestCase("small_block2", []int{3, 10, 12}), // small block with txs across 5 smaller block parts
 }
 
 type testCase struct {
@@ -110,9 +110,13 @@ func runReplayTest(t *testing.T, cs *ConsensusState, walDir string, newBlockCh c
 	cs.Wait()
 }
 
+func toPV(pv PrivValidator) *types.PrivValidator {
+	return pv.(*types.PrivValidator)
+}
+
 func setupReplayTest(thisCase *testCase, nLines int, crashAfter bool) (*ConsensusState, chan interface{}, string, string) {
 	fmt.Println("-------------------------------------")
-	log.Notice(Fmt("Starting replay test of %d lines of WAL (crash before write)", nLines))
+	log.Notice(Fmt("Starting replay test of %d lines of WAL. Crash after = %v", nLines, crashAfter))
 
 	lineStep := nLines
 	if crashAfter {
@@ -128,10 +132,10 @@ func setupReplayTest(thisCase *testCase, nLines int, crashAfter bool) (*Consensu
 	cs := fixedConsensusStateDummy()
 
 	// set the last step according to when we crashed vs the wal
-	cs.privValidator.LastHeight = 1 // first block
-	cs.privValidator.LastStep = thisCase.stepMap[lineStep]
+	toPV(cs.privValidator).LastHeight = 1 // first block
+	toPV(cs.privValidator).LastStep = thisCase.stepMap[lineStep]
 
-	fmt.Println("LAST STEP", cs.privValidator.LastStep)
+	log.Warn("setupReplayTest", "LastStep", toPV(cs.privValidator).LastStep)
 
 	newBlockCh := subscribeToEvent(cs.evsw, "tester", types.EventStringNewBlock(), 1)
 
@@ -168,8 +172,8 @@ func TestReplayCrashBeforeWritePropose(t *testing.T) {
 		if err != nil {
 			t.Fatalf("Error reading json data: %v", err)
 		}
-		cs.privValidator.LastSignBytes = types.SignBytes(cs.state.ChainID, proposal.Proposal)
-		cs.privValidator.LastSignature = proposal.Proposal.Signature
+		toPV(cs.privValidator).LastSignBytes = types.SignBytes(cs.state.ChainID, proposal.Proposal)
+		toPV(cs.privValidator).LastSignature = proposal.Proposal.Signature
 		runReplayTest(t, cs, walDir, newBlockCh, thisCase, lineNum)
 	}
 }
@@ -187,8 +191,8 @@ func TestReplayCrashBeforeWritePrevote(t *testing.T) {
 			if err != nil {
 				t.Fatalf("Error reading json data: %v", err)
 			}
-			cs.privValidator.LastSignBytes = types.SignBytes(cs.state.ChainID, vote.Vote)
-			cs.privValidator.LastSignature = vote.Vote.Signature
+			toPV(cs.privValidator).LastSignBytes = types.SignBytes(cs.state.ChainID, vote.Vote)
+			toPV(cs.privValidator).LastSignature = vote.Vote.Signature
 		})
 		runReplayTest(t, cs, walDir, newBlockCh, thisCase, lineNum)
 	}
@@ -207,8 +211,8 @@ func TestReplayCrashBeforeWritePrecommit(t *testing.T) {
 			if err != nil {
 				t.Fatalf("Error reading json data: %v", err)
 			}
-			cs.privValidator.LastSignBytes = types.SignBytes(cs.state.ChainID, vote.Vote)
-			cs.privValidator.LastSignature = vote.Vote.Signature
+			toPV(cs.privValidator).LastSignBytes = types.SignBytes(cs.state.ChainID, vote.Vote)
+			toPV(cs.privValidator).LastSignature = vote.Vote.Signature
 		})
 		runReplayTest(t, cs, walDir, newBlockCh, thisCase, lineNum)
 	}
diff --git a/consensus/state.go b/consensus/state.go
index e9dd2f97..e5580f19 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -209,6 +209,12 @@ func (ti *timeoutInfo) String() string {
 	return fmt.Sprintf("%v ; %d/%d %v", ti.Duration, ti.Height, ti.Round, ti.Step)
 }
 
+type PrivValidator interface {
+	GetAddress() []byte
+	SignVote(chainID string, vote *types.Vote) error
+	SignProposal(chainID string, proposal *types.Proposal) error
+}
+
 // Tracks consensus state across block heights and rounds.
 type ConsensusState struct {
 	BaseService
@@ -217,7 +223,7 @@ type ConsensusState struct {
 	proxyAppConn  proxy.AppConnConsensus
 	blockStore    *bc.BlockStore
 	mempool       *mempl.Mempool
-	privValidator *types.PrivValidator
+	privValidator PrivValidator
 
 	mtx sync.Mutex
 	RoundState
@@ -236,6 +242,11 @@ type ConsensusState struct {
 	replayMode bool // so we don't log signing errors during replay
 
 	nSteps int // used for testing to limit the number of transitions the state makes
+
+	// allow certain function to be overwritten for testing
+	decideProposal func(height, round int)
+	doPrevote      func(height, round int)
+	setProposal    func(proposal *types.Proposal) error
 }
 
 func NewConsensusState(config cfg.Config, state *sm.State, proxyAppConn proxy.AppConnConsensus, blockStore *bc.BlockStore, mempool *mempl.Mempool) *ConsensusState {
@@ -251,6 +262,11 @@ func NewConsensusState(config cfg.Config, state *sm.State, proxyAppConn proxy.Ap
 		tockChan:         make(chan timeoutInfo, tickTockBufferSize),
 		timeoutParams:    InitTimeoutParamsFromConfig(config),
 	}
+	// set function defaults (may be overwritten before calling Start)
+	cs.decideProposal = cs.defaultDecideProposal
+	cs.doPrevote = cs.defaultDoPrevote
+	cs.setProposal = cs.defaultSetProposal
+
 	cs.updateToState(state)
 	// Don't call scheduleRound0 yet.
 	// We do that upon Start().
@@ -295,7 +311,7 @@ func (cs *ConsensusState) GetValidators() (int, []*types.Validator) {
 	return cs.state.LastBlockHeight, cs.state.Validators.Copy().Validators
 }
 
-func (cs *ConsensusState) SetPrivValidator(priv *types.PrivValidator) {
+func (cs *ConsensusState) SetPrivValidator(priv PrivValidator) {
 	cs.mtx.Lock()
 	defer cs.mtx.Unlock()
 	cs.privValidator = priv
@@ -374,15 +390,15 @@ func (cs *ConsensusState) OpenWAL(walDir string) (err error) {
 // TODO: should these return anything or let callers just use events?
 
 // May block on send if queue is full.
-func (cs *ConsensusState) AddVote(valIndex int, vote *types.Vote, peerKey string) (added bool, address []byte, err error) {
+func (cs *ConsensusState) AddVote(vote *types.Vote, peerKey string) (added bool, err error) {
 	if peerKey == "" {
-		cs.internalMsgQueue <- msgInfo{&VoteMessage{valIndex, vote}, ""}
+		cs.internalMsgQueue <- msgInfo{&VoteMessage{vote}, ""}
 	} else {
-		cs.peerMsgQueue <- msgInfo{&VoteMessage{valIndex, vote}, peerKey}
+		cs.peerMsgQueue <- msgInfo{&VoteMessage{vote}, peerKey}
 	}
 
 	// TODO: wait for event?!
-	return false, nil, nil
+	return false, nil
 }
 
 // May block on send if queue is full.
@@ -472,11 +488,11 @@ func (cs *ConsensusState) reconstructLastCommit(state *sm.State) {
 	}
 	seenCommit := cs.blockStore.LoadSeenCommit(state.LastBlockHeight)
 	lastPrecommits := types.NewVoteSet(cs.config.GetString("chain_id"), state.LastBlockHeight, seenCommit.Round(), types.VoteTypePrecommit, state.LastValidators)
-	for idx, precommit := range seenCommit.Precommits {
+	for _, precommit := range seenCommit.Precommits {
 		if precommit == nil {
 			continue
 		}
-		added, _, err := lastPrecommits.AddByIndex(idx, precommit)
+		added, err := lastPrecommits.AddVote(precommit)
 		if !added || err != nil {
 			PanicCrisis(Fmt("Failed to reconstruct LastCommit: %v", err))
 		}
@@ -694,7 +710,7 @@ func (cs *ConsensusState) handleMsg(mi msgInfo, rs RoundState) {
 	case *VoteMessage:
 		// attempt to add the vote and dupeout the validator if its a duplicate signature
 		// if the vote gives us a 2/3-any or 2/3-one, we transition
-		err := cs.tryAddVote(msg.ValidatorIndex, msg.Vote, peerKey)
+		err := cs.tryAddVote(msg.Vote, peerKey)
 		if err == ErrAddingVote {
 			// TODO: punish peer
 		}
@@ -825,16 +841,16 @@ func (cs *ConsensusState) enterPropose(height int, round int) {
 		return
 	}
 
-	if !bytes.Equal(cs.Validators.Proposer().Address, cs.privValidator.Address) {
+	if !bytes.Equal(cs.Validators.Proposer().Address, cs.privValidator.GetAddress()) {
 		log.Info("enterPropose: Not our turn to propose", "proposer", cs.Validators.Proposer().Address, "privValidator", cs.privValidator)
 	} else {
 		log.Info("enterPropose: Our turn to propose", "proposer", cs.Validators.Proposer().Address, "privValidator", cs.privValidator)
 		cs.decideProposal(height, round)
-	}
 
+	}
 }
 
-func (cs *ConsensusState) decideProposal(height, round int) {
+func (cs *ConsensusState) defaultDecideProposal(height, round int) {
 	var block *types.Block
 	var blockParts *types.PartSet
 
@@ -851,7 +867,8 @@ func (cs *ConsensusState) decideProposal(height, round int) {
 	}
 
 	// Make proposal
-	proposal := types.NewProposal(height, round, blockParts.Header(), cs.Votes.POLRound())
+	polRound, polBlockID := cs.Votes.POLInfo()
+	proposal := types.NewProposal(height, round, blockParts.Header(), polRound, polBlockID)
 	err := cs.privValidator.SignProposal(cs.state.ChainID, proposal)
 	if err == nil {
 		// Set fields
@@ -874,7 +891,6 @@ func (cs *ConsensusState) decideProposal(height, round int) {
 			log.Warn("enterPropose: Error signing proposal", "height", height, "round", round, "error", err)
 		}
 	}
-
 }
 
 // Returns true if the proposal block is complete &&
@@ -920,8 +936,7 @@ func (cs *ConsensusState) createProposalBlock() (block *types.Block, blockParts
 			Height:         cs.Height,
 			Time:           time.Now(),
 			NumTxs:         len(txs),
-			LastBlockHash:  cs.state.LastBlockHash,
-			LastBlockParts: cs.state.LastBlockParts,
+			LastBlockID:    cs.state.LastBlockID,
 			ValidatorsHash: cs.state.Validators.Hash(),
 			AppHash:        cs.state.AppHash, // state merkle root of txs from the previous block.
 		},
@@ -931,7 +946,7 @@ func (cs *ConsensusState) createProposalBlock() (block *types.Block, blockParts
 		},
 	}
 	block.FillHeader()
-	blockParts = block.MakePartSet()
+	blockParts = block.MakePartSet(cs.config.GetInt("block_part_size"))
 
 	return block, blockParts
 }
@@ -972,10 +987,10 @@ func (cs *ConsensusState) enterPrevote(height int, round int) {
 	// (so we have more time to try and collect +2/3 prevotes for a single block)
 }
 
-func (cs *ConsensusState) doPrevote(height int, round int) {
+func (cs *ConsensusState) defaultDoPrevote(height int, round int) {
 	// If a block is locked, prevote that.
 	if cs.LockedBlock != nil {
-		log.Info("enterPrevote: Block was locked")
+		log.Notice("enterPrevote: Block was locked")
 		cs.signAddVote(types.VoteTypePrevote, cs.LockedBlock.Hash(), cs.LockedBlockParts.Header())
 		return
 	}
@@ -1046,14 +1061,14 @@ func (cs *ConsensusState) enterPrecommit(height int, round int) {
 		cs.newStep()
 	}()
 
-	hash, partsHeader, ok := cs.Votes.Prevotes(round).TwoThirdsMajority()
+	blockID, ok := cs.Votes.Prevotes(round).TwoThirdsMajority()
 
 	// If we don't have a polka, we must precommit nil
 	if !ok {
 		if cs.LockedBlock != nil {
-			log.Info("enterPrecommit: No +2/3 prevotes during enterPrecommit while we're locked. Precommitting nil")
+			log.Notice("enterPrecommit: No +2/3 prevotes during enterPrecommit while we're locked. Precommitting nil")
 		} else {
-			log.Info("enterPrecommit: No +2/3 prevotes during enterPrecommit. Precommitting nil.")
+			log.Notice("enterPrecommit: No +2/3 prevotes during enterPrecommit. Precommitting nil.")
 		}
 		cs.signAddVote(types.VoteTypePrecommit, nil, types.PartSetHeader{})
 		return
@@ -1063,12 +1078,13 @@ func (cs *ConsensusState) enterPrecommit(height int, round int) {
 	types.FireEventPolka(cs.evsw, cs.RoundStateEvent())
 
 	// the latest POLRound should be this round
-	if cs.Votes.POLRound() < round {
-		PanicSanity(Fmt("This POLRound should be %v but got %", round, cs.Votes.POLRound()))
+	polRound, _ := cs.Votes.POLInfo()
+	if polRound < round {
+		PanicSanity(Fmt("This POLRound should be %v but got %", round, polRound))
 	}
 
 	// +2/3 prevoted nil. Unlock and precommit nil.
-	if len(hash) == 0 {
+	if len(blockID.Hash) == 0 {
 		if cs.LockedBlock == nil {
 			log.Notice("enterPrecommit: +2/3 prevoted for nil.")
 		} else {
@@ -1085,17 +1101,17 @@ func (cs *ConsensusState) enterPrecommit(height int, round int) {
 	// At this point, +2/3 prevoted for a particular block.
 
 	// If we're already locked on that block, precommit it, and update the LockedRound
-	if cs.LockedBlock.HashesTo(hash) {
+	if cs.LockedBlock.HashesTo(blockID.Hash) {
 		log.Notice("enterPrecommit: +2/3 prevoted locked block. Relocking")
 		cs.LockedRound = round
 		types.FireEventRelock(cs.evsw, cs.RoundStateEvent())
-		cs.signAddVote(types.VoteTypePrecommit, hash, partsHeader)
+		cs.signAddVote(types.VoteTypePrecommit, blockID.Hash, blockID.PartsHeader)
 		return
 	}
 
 	// If +2/3 prevoted for proposal block, stage and precommit it
-	if cs.ProposalBlock.HashesTo(hash) {
-		log.Notice("enterPrecommit: +2/3 prevoted proposal block. Locking", "hash", hash)
+	if cs.ProposalBlock.HashesTo(blockID.Hash) {
+		log.Notice("enterPrecommit: +2/3 prevoted proposal block. Locking", "hash", blockID.Hash)
 		// Validate the block.
 		if err := cs.state.ValidateBlock(cs.ProposalBlock); err != nil {
 			PanicConsensus(Fmt("enterPrecommit: +2/3 prevoted for an invalid block: %v", err))
@@ -1104,7 +1120,7 @@ func (cs *ConsensusState) enterPrecommit(height int, round int) {
 		cs.LockedBlock = cs.ProposalBlock
 		cs.LockedBlockParts = cs.ProposalBlockParts
 		types.FireEventLock(cs.evsw, cs.RoundStateEvent())
-		cs.signAddVote(types.VoteTypePrecommit, hash, partsHeader)
+		cs.signAddVote(types.VoteTypePrecommit, blockID.Hash, blockID.PartsHeader)
 		return
 	}
 
@@ -1115,9 +1131,9 @@ func (cs *ConsensusState) enterPrecommit(height int, round int) {
 	cs.LockedRound = 0
 	cs.LockedBlock = nil
 	cs.LockedBlockParts = nil
-	if !cs.ProposalBlockParts.HasHeader(partsHeader) {
+	if !cs.ProposalBlockParts.HasHeader(blockID.PartsHeader) {
 		cs.ProposalBlock = nil
-		cs.ProposalBlockParts = types.NewPartSetFromHeader(partsHeader)
+		cs.ProposalBlockParts = types.NewPartSetFromHeader(blockID.PartsHeader)
 	}
 	types.FireEventUnlock(cs.evsw, cs.RoundStateEvent())
 	cs.signAddVote(types.VoteTypePrecommit, nil, types.PartSetHeader{})
@@ -1165,7 +1181,7 @@ func (cs *ConsensusState) enterCommit(height int, commitRound int) {
 		cs.tryFinalizeCommit(height)
 	}()
 
-	hash, partsHeader, ok := cs.Votes.Precommits(commitRound).TwoThirdsMajority()
+	blockID, ok := cs.Votes.Precommits(commitRound).TwoThirdsMajority()
 	if !ok {
 		PanicSanity("RunActionCommit() expects +2/3 precommits")
 	}
@@ -1173,18 +1189,18 @@ func (cs *ConsensusState) enterCommit(height int, commitRound int) {
 	// The Locked* fields no longer matter.
 	// Move them over to ProposalBlock if they match the commit hash,
 	// otherwise they'll be cleared in updateToState.
-	if cs.LockedBlock.HashesTo(hash) {
+	if cs.LockedBlock.HashesTo(blockID.Hash) {
 		cs.ProposalBlock = cs.LockedBlock
 		cs.ProposalBlockParts = cs.LockedBlockParts
 	}
 
 	// If we don't have the block being committed, set up to get it.
-	if !cs.ProposalBlock.HashesTo(hash) {
-		if !cs.ProposalBlockParts.HasHeader(partsHeader) {
+	if !cs.ProposalBlock.HashesTo(blockID.Hash) {
+		if !cs.ProposalBlockParts.HasHeader(blockID.PartsHeader) {
 			// We're getting the wrong block.
 			// Set up ProposalBlockParts and keep waiting.
 			cs.ProposalBlock = nil
-			cs.ProposalBlockParts = types.NewPartSetFromHeader(partsHeader)
+			cs.ProposalBlockParts = types.NewPartSetFromHeader(blockID.PartsHeader)
 		} else {
 			// We just need to keep waiting.
 		}
@@ -1197,12 +1213,12 @@ func (cs *ConsensusState) tryFinalizeCommit(height int) {
 		PanicSanity(Fmt("tryFinalizeCommit() cs.Height: %v vs height: %v", cs.Height, height))
 	}
 
-	hash, _, ok := cs.Votes.Precommits(cs.CommitRound).TwoThirdsMajority()
-	if !ok || len(hash) == 0 {
+	blockID, ok := cs.Votes.Precommits(cs.CommitRound).TwoThirdsMajority()
+	if !ok || len(blockID.Hash) == 0 {
 		log.Warn("Attempt to finalize failed. There was no +2/3 majority, or +2/3 was for <nil>.")
 		return
 	}
-	if !cs.ProposalBlock.HashesTo(hash) {
+	if !cs.ProposalBlock.HashesTo(blockID.Hash) {
 		// TODO: this happens every time if we're not a validator (ugly logs)
 		// TODO: ^^ wait, why does it matter that we're a validator?
 		log.Warn("Attempt to finalize failed. We don't have the commit block.")
@@ -1219,16 +1235,16 @@ func (cs *ConsensusState) finalizeCommit(height int) {
 		return
 	}
 
-	hash, header, ok := cs.Votes.Precommits(cs.CommitRound).TwoThirdsMajority()
+	blockID, ok := cs.Votes.Precommits(cs.CommitRound).TwoThirdsMajority()
 	block, blockParts := cs.ProposalBlock, cs.ProposalBlockParts
 
 	if !ok {
 		PanicSanity(Fmt("Cannot finalizeCommit, commit does not have two thirds majority"))
 	}
-	if !blockParts.HasHeader(header) {
+	if !blockParts.HasHeader(blockID.PartsHeader) {
 		PanicSanity(Fmt("Expected ProposalBlockParts header to be commit header"))
 	}
-	if !block.HashesTo(hash) {
+	if !block.HashesTo(blockID.Hash) {
 		PanicSanity(Fmt("Cannot finalizeCommit, ProposalBlock does not hash to commit hash"))
 	}
 	if err := cs.state.ValidateBlock(block); err != nil {
@@ -1321,8 +1337,9 @@ func (cs *ConsensusState) commitStateUpdateMempool(s *sm.State, block *types.Blo
 
 //-----------------------------------------------------------------------------
 
-func (cs *ConsensusState) setProposal(proposal *types.Proposal) error {
+func (cs *ConsensusState) defaultSetProposal(proposal *types.Proposal) error {
 	// Already have one
+	// TODO: possibly catch double proposals
 	if cs.Proposal != nil {
 		return nil
 	}
@@ -1390,15 +1407,15 @@ func (cs *ConsensusState) addProposalBlockPart(height int, part *types.Part, ver
 }
 
 // Attempt to add the vote. if its a duplicate signature, dupeout the validator
-func (cs *ConsensusState) tryAddVote(valIndex int, vote *types.Vote, peerKey string) error {
-	_, _, err := cs.addVote(valIndex, vote, peerKey)
+func (cs *ConsensusState) tryAddVote(vote *types.Vote, peerKey string) error {
+	_, err := cs.addVote(vote, peerKey)
 	if err != nil {
 		// If the vote height is off, we'll just ignore it,
 		// But if it's a conflicting sig, broadcast evidence tx for slashing.
 		// If it's otherwise invalid, punish peer.
 		if err == ErrVoteHeightMismatch {
 			return err
-		} else if _, ok := err.(*types.ErrVoteConflictingSignature); ok {
+		} else if _, ok := err.(*types.ErrVoteConflictingVotes); ok {
 			if peerKey == "" {
 				log.Warn("Found conflicting vote from ourselves. Did you unsafe_reset a validator?", "height", vote.Height, "round", vote.Round, "type", vote.Type)
 				return err
@@ -1424,7 +1441,7 @@ func (cs *ConsensusState) tryAddVote(valIndex int, vote *types.Vote, peerKey str
 
 //-----------------------------------------------------------------------------
 
-func (cs *ConsensusState) addVote(valIndex int, vote *types.Vote, peerKey string) (added bool, address []byte, err error) {
+func (cs *ConsensusState) addVote(vote *types.Vote, peerKey string) (added bool, err error) {
 	log.Debug("addVote", "voteHeight", vote.Height, "voteType", vote.Type, "csHeight", cs.Height)
 
 	// A precommit for the previous height?
@@ -1432,13 +1449,12 @@ func (cs *ConsensusState) addVote(valIndex int, vote *types.Vote, peerKey string
 		if !(cs.Step == RoundStepNewHeight && vote.Type == types.VoteTypePrecommit) {
 			// TODO: give the reason ..
 			// fmt.Errorf("tryAddVote: Wrong height, not a LastCommit straggler commit.")
-			return added, nil, ErrVoteHeightMismatch
+			return added, ErrVoteHeightMismatch
 		}
-		added, address, err = cs.LastCommit.AddByIndex(valIndex, vote)
+		added, err = cs.LastCommit.AddVote(vote)
 		if added {
 			log.Info(Fmt("Added to lastPrecommits: %v", cs.LastCommit.StringShort()))
-			types.FireEventVote(cs.evsw, types.EventDataVote{valIndex, address, vote})
-
+			types.FireEventVote(cs.evsw, types.EventDataVote{vote})
 		}
 		return
 	}
@@ -1446,9 +1462,9 @@ func (cs *ConsensusState) addVote(valIndex int, vote *types.Vote, peerKey string
 	// A prevote/precommit for this height?
 	if vote.Height == cs.Height {
 		height := cs.Height
-		added, address, err = cs.Votes.AddByIndex(valIndex, vote, peerKey)
+		added, err = cs.Votes.AddVote(vote, peerKey)
 		if added {
-			types.FireEventVote(cs.evsw, types.EventDataVote{valIndex, address, vote})
+			types.FireEventVote(cs.evsw, types.EventDataVote{vote})
 
 			switch vote.Type {
 			case types.VoteTypePrevote:
@@ -1460,8 +1476,8 @@ func (cs *ConsensusState) addVote(valIndex int, vote *types.Vote, peerKey string
 				// we'll still enterNewRound(H,vote.R) and enterPrecommit(H,vote.R) to process it
 				// there.
 				if (cs.LockedBlock != nil) && (cs.LockedRound < vote.Round) && (vote.Round <= cs.Round) {
-					hash, _, ok := prevotes.TwoThirdsMajority()
-					if ok && !cs.LockedBlock.HashesTo(hash) {
+					blockID, ok := prevotes.TwoThirdsMajority()
+					if ok && !cs.LockedBlock.HashesTo(blockID.Hash) {
 						log.Notice("Unlocking because of POL.", "lockedRound", cs.LockedRound, "POLRound", vote.Round)
 						cs.LockedRound = 0
 						cs.LockedBlock = nil
@@ -1487,9 +1503,9 @@ func (cs *ConsensusState) addVote(valIndex int, vote *types.Vote, peerKey string
 			case types.VoteTypePrecommit:
 				precommits := cs.Votes.Precommits(vote.Round)
 				log.Info("Added to precommit", "vote", vote, "precommits", precommits.StringShort())
-				hash, _, ok := precommits.TwoThirdsMajority()
+				blockID, ok := precommits.TwoThirdsMajority()
 				if ok {
-					if len(hash) == 0 {
+					if len(blockID.Hash) == 0 {
 						cs.enterNewRound(height, vote.Round+1)
 					} else {
 						cs.enterNewRound(height, vote.Round)
@@ -1518,12 +1534,16 @@ func (cs *ConsensusState) addVote(valIndex int, vote *types.Vote, peerKey string
 }
 
 func (cs *ConsensusState) signVote(type_ byte, hash []byte, header types.PartSetHeader) (*types.Vote, error) {
+	// TODO: store our index in the cs so we don't have to do this every time
+	addr := cs.privValidator.GetAddress()
+	valIndex, _ := cs.Validators.GetByAddress(addr)
 	vote := &types.Vote{
+		ValidatorAddress: addr,
+		ValidatorIndex:   valIndex,
 		Height:           cs.Height,
 		Round:            cs.Round,
 		Type:             type_,
-		BlockHash:        hash,
-		BlockPartsHeader: header,
+		BlockID:          types.BlockID{hash, header},
 	}
 	err := cs.privValidator.SignVote(cs.state.ChainID, vote)
 	return vote, err
@@ -1531,21 +1551,18 @@ func (cs *ConsensusState) signVote(type_ byte, hash []byte, header types.PartSet
 
 // sign the vote and publish on internalMsgQueue
 func (cs *ConsensusState) signAddVote(type_ byte, hash []byte, header types.PartSetHeader) *types.Vote {
-
-	if cs.privValidator == nil || !cs.Validators.HasAddress(cs.privValidator.Address) {
+	if cs.privValidator == nil || !cs.Validators.HasAddress(cs.privValidator.GetAddress()) {
 		return nil
 	}
 	vote, err := cs.signVote(type_, hash, header)
 	if err == nil {
-		// TODO: store our index in the cs so we don't have to do this every time
-		valIndex, _ := cs.Validators.GetByAddress(cs.privValidator.Address)
-		cs.sendInternalMessage(msgInfo{&VoteMessage{valIndex, vote}, ""})
+		cs.sendInternalMessage(msgInfo{&VoteMessage{vote}, ""})
 		log.Info("Signed and pushed vote", "height", cs.Height, "round", cs.Round, "vote", vote, "error", err)
 		return vote
 	} else {
-		if !cs.replayMode {
-			log.Warn("Error signing vote", "height", cs.Height, "round", cs.Round, "vote", vote, "error", err)
-		}
+		//if !cs.replayMode {
+		log.Warn("Error signing vote", "height", cs.Height, "round", cs.Round, "vote", vote, "error", err)
+		//}
 		return nil
 	}
 }
diff --git a/consensus/state_test.go b/consensus/state_test.go
index a09ab16f..d3eef59f 100644
--- a/consensus/state_test.go
+++ b/consensus/state_test.go
@@ -30,7 +30,7 @@ x * TestBadProposal - 2 vals, bad proposal (bad block state hash), should prevot
 FullRoundSuite
 x * TestFullRound1 - 1 val, full successful round
 x * TestFullRoundNil - 1 val, full round of nil
-x * TestFullRound2 - 2 vals, both required for fuill round
+x * TestFullRound2 - 2 vals, both required for full round
 LockSuite
 x * TestLockNoPOL - 2 vals, 4 rounds. one val locked, precommits nil every round except first.
 x * TestLockPOLRelock - 4 vals, one precommits, other 3 polka at next round, so we unlock and precomit the polka
@@ -66,15 +66,15 @@ func TestProposerSelection0(t *testing.T) {
 
 	// lets commit a block and ensure proposer for the next height is correct
 	prop := cs1.GetRoundState().Validators.Proposer()
-	if !bytes.Equal(prop.Address, cs1.privValidator.Address) {
-		panic(Fmt("expected proposer to be validator %d. Got %X", 0, prop.Address))
+	if !bytes.Equal(prop.Address, cs1.privValidator.GetAddress()) {
+		t.Fatalf("expected proposer to be validator %d. Got %X", 0, prop.Address)
 	}
 
 	// wait for complete proposal
 	<-proposalCh
 
 	rs := cs1.GetRoundState()
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), nil, vss[1:]...)
+	signAddVotes(cs1, types.VoteTypePrecommit, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), vss[1:]...)
 
 	// wait for new round so next validator is set
 	<-newRoundCh
@@ -106,7 +106,7 @@ func TestProposerSelection2(t *testing.T) {
 		}
 
 		rs := cs1.GetRoundState()
-		signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, rs.ProposalBlockParts.Header(), nil, vss[1:]...)
+		signAddVotes(cs1, types.VoteTypePrecommit, nil, rs.ProposalBlockParts.Header(), vss[1:]...)
 		<-newRoundCh // wait for the new round event each round
 
 		incrementRound(vss[1:]...)
@@ -179,12 +179,14 @@ func TestEnterProposeYesPrivValidator(t *testing.T) {
 func TestBadProposal(t *testing.T) {
 	cs1, vss := randConsensusState(2)
 	height, round := cs1.Height, cs1.Round
-	cs2 := vss[1]
+	vs2 := vss[1]
+
+	partSize := config.GetInt("block_part_size")
 
 	proposalCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringCompleteProposal(), 1)
 	voteCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringVote(), 1)
 
-	propBlock, _ := cs1.createProposalBlock() //changeProposer(t, cs1, cs2)
+	propBlock, _ := cs1.createProposalBlock() //changeProposer(t, cs1, vs2)
 
 	// make the second validator the proposer by incrementing round
 	round = round + 1
@@ -197,10 +199,10 @@ func TestBadProposal(t *testing.T) {
 	}
 	stateHash[0] = byte((stateHash[0] + 1) % 255)
 	propBlock.AppHash = stateHash
-	propBlockParts := propBlock.MakePartSet()
-	proposal := types.NewProposal(cs2.Height, round, propBlockParts.Header(), -1)
-	if err := cs2.SignProposal(config.GetString("chain_id"), proposal); err != nil {
-		panic("failed to sign bad proposal: " + err.Error())
+	propBlockParts := propBlock.MakePartSet(partSize)
+	proposal := types.NewProposal(vs2.Height, round, propBlockParts.Header(), -1, types.BlockID{})
+	if err := vs2.SignProposal(config.GetString("chain_id"), proposal); err != nil {
+		t.Fatal("failed to sign bad proposal", err)
 	}
 
 	// set the proposal block
@@ -217,14 +219,15 @@ func TestBadProposal(t *testing.T) {
 
 	validatePrevote(t, cs1, round, vss[0], nil)
 
-	// add bad prevote from cs2 and wait for it
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, propBlock.Hash(), propBlock.MakePartSet().Header(), voteCh)
+	// add bad prevote from vs2 and wait for it
+	signAddVotes(cs1, types.VoteTypePrevote, propBlock.Hash(), propBlock.MakePartSet(partSize).Header(), vs2)
+	<-voteCh
 
 	// wait for precommit
 	<-voteCh
 
 	validatePrecommit(t, cs1, round, 0, vss[0], nil, nil)
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, propBlock.Hash(), propBlock.MakePartSet().Header(), voteCh)
+	signAddVotes(cs1, types.VoteTypePrecommit, propBlock.Hash(), propBlock.MakePartSet(partSize).Header(), vs2)
 }
 
 //----------------------------------------------------------------------------------------------------
@@ -281,7 +284,7 @@ func TestFullRoundNil(t *testing.T) {
 // where the first validator has to wait for votes from the second
 func TestFullRound2(t *testing.T) {
 	cs1, vss := randConsensusState(2)
-	cs2 := vss[1]
+	vs2 := vss[1]
 	height, round := cs1.Height, cs1.Round
 
 	voteCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringVote(), 1)
@@ -296,8 +299,9 @@ func TestFullRound2(t *testing.T) {
 	rs := cs1.GetRoundState()
 	propBlockHash, propPartsHeader := rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header()
 
-	// prevote arrives from cs2:
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, propBlockHash, propPartsHeader, voteCh)
+	// prevote arrives from vs2:
+	signAddVotes(cs1, types.VoteTypePrevote, propBlockHash, propPartsHeader, vs2)
+	<-voteCh
 
 	<-voteCh //precommit
 
@@ -306,8 +310,9 @@ func TestFullRound2(t *testing.T) {
 
 	// we should be stuck in limbo waiting for more precommits
 
-	// precommit arrives from cs2:
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, propBlockHash, propPartsHeader, voteCh)
+	// precommit arrives from vs2:
+	signAddVotes(cs1, types.VoteTypePrecommit, propBlockHash, propPartsHeader, vs2)
+	<-voteCh
 
 	// wait to finish commit, propose in next height
 	<-newBlockCh
@@ -320,9 +325,11 @@ func TestFullRound2(t *testing.T) {
 // two vals take turns proposing. val1 locks on first one, precommits nil on everything else
 func TestLockNoPOL(t *testing.T) {
 	cs1, vss := randConsensusState(2)
-	cs2 := vss[1]
+	vs2 := vss[1]
 	height := cs1.Height
 
+	partSize := config.GetInt("block_part_size")
+
 	timeoutProposeCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutPropose(), 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutWait(), 1)
 	voteCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringVote(), 1)
@@ -344,8 +351,9 @@ func TestLockNoPOL(t *testing.T) {
 	<-voteCh // prevote
 
 	// we should now be stuck in limbo forever, waiting for more prevotes
-	// prevote arrives from cs2:
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), voteCh)
+	// prevote arrives from vs2:
+	signAddVotes(cs1, types.VoteTypePrevote, cs1.ProposalBlock.Hash(), cs1.ProposalBlockParts.Header(), vs2)
+	<-voteCh // prevote
 
 	<-voteCh // precommit
 
@@ -358,7 +366,8 @@ func TestLockNoPOL(t *testing.T) {
 	hash := make([]byte, len(theBlockHash))
 	copy(hash, theBlockHash)
 	hash[0] = byte((hash[0] + 1) % 255)
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, hash, rs.ProposalBlock.MakePartSet().Header(), voteCh)
+	signAddVotes(cs1, types.VoteTypePrecommit, hash, rs.ProposalBlock.MakePartSet(partSize).Header(), vs2)
+	<-voteCh // precommit
 
 	// (note we're entering precommit for a second time this round)
 	// but with invalid args. then we enterPrecommitWait, and the timeout to new round
@@ -372,7 +381,7 @@ func TestLockNoPOL(t *testing.T) {
 		Round2 (cs1, B) // B B2
 	*/
 
-	incrementRound(cs2)
+	incrementRound(vs2)
 
 	// now we're on a new round and not the proposer, so wait for timeout
 	re = <-timeoutProposeCh
@@ -389,7 +398,8 @@ func TestLockNoPOL(t *testing.T) {
 	validatePrevote(t, cs1, 1, vss[0], rs.LockedBlock.Hash())
 
 	// add a conflicting prevote from the other validator
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, hash, rs.ProposalBlock.MakePartSet().Header(), voteCh)
+	signAddVotes(cs1, types.VoteTypePrevote, hash, rs.ProposalBlock.MakePartSet(partSize).Header(), vs2)
+	<-voteCh
 
 	// now we're going to enter prevote again, but with invalid args
 	// and then prevote wait, which should timeout. then wait for precommit
@@ -401,9 +411,10 @@ func TestLockNoPOL(t *testing.T) {
 	// we should precommit nil and be locked on the proposal
 	validatePrecommit(t, cs1, 1, 0, vss[0], nil, theBlockHash)
 
-	// add conflicting precommit from cs2
+	// add conflicting precommit from vs2
 	// NOTE: in practice we should never get to a point where there are precommits for different blocks at the same round
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, hash, rs.ProposalBlock.MakePartSet().Header(), voteCh)
+	signAddVotes(cs1, types.VoteTypePrecommit, hash, rs.ProposalBlock.MakePartSet(partSize).Header(), vs2)
+	<-voteCh
 
 	// (note we're entering precommit for a second time this round, but with invalid args
 	// then we enterPrecommitWait and timeout into NewRound
@@ -412,10 +423,10 @@ func TestLockNoPOL(t *testing.T) {
 	<-newRoundCh
 	log.Notice("#### ONTO ROUND 2")
 	/*
-		Round3 (cs2, _) // B, B2
+		Round3 (vs2, _) // B, B2
 	*/
 
-	incrementRound(cs2)
+	incrementRound(vs2)
 
 	re = <-proposalCh
 	rs = re.(types.EventDataRoundState).RoundState.(*RoundState)
@@ -429,33 +440,36 @@ func TestLockNoPOL(t *testing.T) {
 
 	validatePrevote(t, cs1, 2, vss[0], rs.LockedBlock.Hash())
 
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, hash, rs.ProposalBlock.MakePartSet().Header(), voteCh)
+	signAddVotes(cs1, types.VoteTypePrevote, hash, rs.ProposalBlock.MakePartSet(partSize).Header(), vs2)
+	<-voteCh
 
 	<-timeoutWaitCh // prevote wait
 	<-voteCh        // precommit
 
-	validatePrecommit(t, cs1, 2, 0, vss[0], nil, theBlockHash)                                                  // precommit nil but be locked on proposal
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, hash, rs.ProposalBlock.MakePartSet().Header(), voteCh) // NOTE: conflicting precommits at same height
+	validatePrecommit(t, cs1, 2, 0, vss[0], nil, theBlockHash) // precommit nil but be locked on proposal
+
+	signAddVotes(cs1, types.VoteTypePrecommit, hash, rs.ProposalBlock.MakePartSet(partSize).Header(), vs2) // NOTE: conflicting precommits at same height
+	<-voteCh
 
 	<-timeoutWaitCh
 
 	// before we time out into new round, set next proposal block
-	prop, propBlock := decideProposal(cs1, cs2, cs2.Height, cs2.Round+1)
+	prop, propBlock := decideProposal(cs1, vs2, vs2.Height, vs2.Round+1)
 	if prop == nil || propBlock == nil {
-		panic("Failed to create proposal block with cs2")
+		t.Fatal("Failed to create proposal block with vs2")
 	}
 
-	incrementRound(cs2)
+	incrementRound(vs2)
 
 	<-newRoundCh
 	log.Notice("#### ONTO ROUND 3")
 	/*
-		Round4 (cs2, C) // B C // B C
+		Round4 (vs2, C) // B C // B C
 	*/
 
 	// now we're on a new round and not the proposer
 	// so set the proposal block
-	cs1.SetProposalAndBlock(prop, propBlock, propBlock.MakePartSet(), "")
+	cs1.SetProposalAndBlock(prop, propBlock, propBlock.MakePartSet(partSize), "")
 
 	<-proposalCh
 	<-voteCh // prevote
@@ -463,19 +477,24 @@ func TestLockNoPOL(t *testing.T) {
 	// prevote for locked block (not proposal)
 	validatePrevote(t, cs1, 0, vss[0], cs1.LockedBlock.Hash())
 
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, propBlock.Hash(), propBlock.MakePartSet().Header(), voteCh)
+	signAddVotes(cs1, types.VoteTypePrevote, propBlock.Hash(), propBlock.MakePartSet(partSize).Header(), vs2)
+	<-voteCh
 
 	<-timeoutWaitCh
 	<-voteCh
 
-	validatePrecommit(t, cs1, 2, 0, vss[0], nil, theBlockHash)                                                       // precommit nil but locked on proposal
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, propBlock.Hash(), propBlock.MakePartSet().Header(), voteCh) // NOTE: conflicting precommits at same height
+	validatePrecommit(t, cs1, 2, 0, vss[0], nil, theBlockHash) // precommit nil but locked on proposal
+
+	signAddVotes(cs1, types.VoteTypePrecommit, propBlock.Hash(), propBlock.MakePartSet(partSize).Header(), vs2) // NOTE: conflicting precommits at same height
+	<-voteCh
 }
 
 // 4 vals, one precommits, other 3 polka at next round, so we unlock and precomit the polka
 func TestLockPOLRelock(t *testing.T) {
 	cs1, vss := randConsensusState(4)
-	cs2, cs3, cs4 := vss[1], vss[2], vss[3]
+	vs2, vs3, vs4 := vss[1], vss[2], vss[3]
+
+	partSize := config.GetInt("block_part_size")
 
 	timeoutProposeCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutPropose(), 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutWait(), 1)
@@ -484,14 +503,14 @@ func TestLockPOLRelock(t *testing.T) {
 	newRoundCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewRound(), 1)
 	newBlockCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewBlockHeader(), 1)
 
-	log.Debug("cs2 last round", "lr", cs2.PrivValidator.LastRound)
+	log.Debug("vs2 last round", "lr", vs2.PrivValidator.LastRound)
 
 	// everything done from perspective of cs1
 
 	/*
 		Round1 (cs1, B) // B B B B// B nil B nil
 
-		eg. cs2 and cs4 didn't see the 2/3 prevotes
+		eg. vs2 and vs4 didn't see the 2/3 prevotes
 	*/
 
 	// start round and wait for propose and prevote
@@ -501,26 +520,27 @@ func TestLockPOLRelock(t *testing.T) {
 	re := <-proposalCh
 	rs := re.(types.EventDataRoundState).RoundState.(*RoundState)
 	theBlockHash := rs.ProposalBlock.Hash()
-	theBlockPartsHeader := rs.ProposalBlockParts.Header()
 
 	<-voteCh // prevote
 
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, theBlockHash, theBlockPartsHeader, voteCh, cs2, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrevote, cs1.ProposalBlock.Hash(), cs1.ProposalBlockParts.Header(), vs2, vs3, vs4)
+	_, _, _ = <-voteCh, <-voteCh, <-voteCh // prevotes
 
 	<-voteCh // our precommit
 	// the proposed block should now be locked and our precommit added
 	validatePrecommit(t, cs1, 0, 0, vss[0], theBlockHash, theBlockHash)
 
 	// add precommits from the rest
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, types.PartSetHeader{}, voteCh, cs2, cs4)
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs3, theBlockHash, theBlockPartsHeader, voteCh)
+	signAddVotes(cs1, types.VoteTypePrecommit, nil, types.PartSetHeader{}, vs2, vs4)
+	signAddVotes(cs1, types.VoteTypePrecommit, cs1.ProposalBlock.Hash(), cs1.ProposalBlockParts.Header(), vs3)
+	_, _, _ = <-voteCh, <-voteCh, <-voteCh // precommits
 
 	// before we timeout to the new round set the new proposal
-	prop, propBlock := decideProposal(cs1, cs2, cs2.Height, cs2.Round+1)
-	propBlockParts := propBlock.MakePartSet()
+	prop, propBlock := decideProposal(cs1, vs2, vs2.Height, vs2.Round+1)
+	propBlockParts := propBlock.MakePartSet(partSize)
 	propBlockHash := propBlock.Hash()
 
-	incrementRound(cs2, cs3, cs4)
+	incrementRound(vs2, vs3, vs4)
 
 	// timeout to new round
 	<-timeoutWaitCh
@@ -532,7 +552,7 @@ func TestLockPOLRelock(t *testing.T) {
 	log.Notice("### ONTO ROUND 1")
 
 	/*
-		Round2 (cs2, C) // B C C C // C C C _)
+		Round2 (vs2, C) // B C C C // C C C _)
 
 		cs1 changes lock!
 	*/
@@ -550,7 +570,8 @@ func TestLockPOLRelock(t *testing.T) {
 	validatePrevote(t, cs1, 0, vss[0], theBlockHash)
 
 	// now lets add prevotes from everyone else for the new block
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, propBlockHash, propBlockParts.Header(), voteCh, cs2, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrevote, propBlockHash, propBlockParts.Header(), vs2, vs3, vs4)
+	_, _, _ = <-voteCh, <-voteCh, <-voteCh // prevotes
 
 	// now either we go to PrevoteWait or Precommit
 	select {
@@ -564,7 +585,8 @@ func TestLockPOLRelock(t *testing.T) {
 	// we should have unlocked and locked on the new block
 	validatePrecommit(t, cs1, 1, 1, vss[0], propBlockHash, propBlockHash)
 
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, propBlockHash, propBlockParts.Header(), voteCh, cs2, cs3)
+	signAddVotes(cs1, types.VoteTypePrecommit, propBlockHash, propBlockParts.Header(), vs2, vs3)
+	_, _ = <-voteCh, <-voteCh
 
 	be := <-newBlockCh
 	b := be.(types.EventDataNewBlockHeader)
@@ -582,14 +604,16 @@ func TestLockPOLRelock(t *testing.T) {
 // 4 vals, one precommits, other 3 polka at next round, so we unlock and precomit the polka
 func TestLockPOLUnlock(t *testing.T) {
 	cs1, vss := randConsensusState(4)
-	cs2, cs3, cs4 := vss[1], vss[2], vss[3]
+	vs2, vs3, vs4 := vss[1], vss[2], vss[3]
+
+	partSize := config.GetInt("block_part_size")
 
 	proposalCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringCompleteProposal(), 1)
 	timeoutProposeCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutPropose(), 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutWait(), 1)
 	newRoundCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewRound(), 1)
 	unlockCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringUnlock(), 1)
-	voteCh := subscribeToVoter(cs1, cs1.privValidator.Address)
+	voteCh := subscribeToVoter(cs1, cs1.privValidator.GetAddress())
 
 	// everything done from perspective of cs1
 
@@ -608,7 +632,7 @@ func TestLockPOLUnlock(t *testing.T) {
 
 	<-voteCh // prevote
 
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), nil, cs2, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrevote, cs1.ProposalBlock.Hash(), cs1.ProposalBlockParts.Header(), vs2, vs3, vs4)
 
 	<-voteCh //precommit
 
@@ -618,14 +642,14 @@ func TestLockPOLUnlock(t *testing.T) {
 	rs = cs1.GetRoundState()
 
 	// add precommits from the rest
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, types.PartSetHeader{}, nil, cs2, cs4)
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs3, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), nil)
+	signAddVotes(cs1, types.VoteTypePrecommit, nil, types.PartSetHeader{}, vs2, vs4)
+	signAddVotes(cs1, types.VoteTypePrecommit, cs1.ProposalBlock.Hash(), cs1.ProposalBlockParts.Header(), vs3)
 
 	// before we time out into new round, set next proposal block
-	prop, propBlock := decideProposal(cs1, cs2, cs2.Height, cs2.Round+1)
-	propBlockParts := propBlock.MakePartSet()
+	prop, propBlock := decideProposal(cs1, vs2, vs2.Height, vs2.Round+1)
+	propBlockParts := propBlock.MakePartSet(partSize)
 
-	incrementRound(cs2, cs3, cs4)
+	incrementRound(vs2, vs3, vs4)
 
 	// timeout to new round
 	re = <-timeoutWaitCh
@@ -638,7 +662,7 @@ func TestLockPOLUnlock(t *testing.T) {
 	<-newRoundCh
 	log.Notice("#### ONTO ROUND 1")
 	/*
-		Round2 (cs2, C) // B nil nil nil // nil nil nil _
+		Round2 (vs2, C) // B nil nil nil // nil nil nil _
 
 		cs1 unlocks!
 	*/
@@ -655,7 +679,7 @@ func TestLockPOLUnlock(t *testing.T) {
 	<-voteCh
 	validatePrevote(t, cs1, 0, vss[0], lockedBlockHash)
 	// now lets add prevotes from everyone else for nil (a polka!)
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, nil, types.PartSetHeader{}, nil, cs2, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrevote, nil, types.PartSetHeader{}, vs2, vs3, vs4)
 
 	// the polka makes us unlock and precommit nil
 	<-unlockCh
@@ -665,7 +689,7 @@ func TestLockPOLUnlock(t *testing.T) {
 	// NOTE: since we don't relock on nil, the lock round is 0
 	validatePrecommit(t, cs1, 1, 0, vss[0], nil, nil)
 
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, types.PartSetHeader{}, nil, cs2, cs3)
+	signAddVotes(cs1, types.VoteTypePrecommit, nil, types.PartSetHeader{}, vs2, vs3)
 	<-newRoundCh
 }
 
@@ -675,13 +699,15 @@ func TestLockPOLUnlock(t *testing.T) {
 // then we see the polka from round 1 but shouldn't unlock
 func TestLockPOLSafety1(t *testing.T) {
 	cs1, vss := randConsensusState(4)
-	cs2, cs3, cs4 := vss[1], vss[2], vss[3]
+	vs2, vs3, vs4 := vss[1], vss[2], vss[3]
+
+	partSize := config.GetInt("block_part_size")
 
 	proposalCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringCompleteProposal(), 1)
 	timeoutProposeCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutPropose(), 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutWait(), 1)
 	newRoundCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewRound(), 1)
-	voteCh := subscribeToVoter(cs1, cs1.privValidator.Address)
+	voteCh := subscribeToVoter(cs1, cs1.privValidator.GetAddress())
 
 	// start round and wait for propose and prevote
 	startTestRound(cs1, cs1.Height, 0)
@@ -695,7 +721,7 @@ func TestLockPOLSafety1(t *testing.T) {
 	validatePrevote(t, cs1, 0, vss[0], propBlock.Hash())
 
 	// the others sign a polka but we don't see it
-	prevotes := signVoteMany(types.VoteTypePrevote, propBlock.Hash(), propBlock.MakePartSet().Header(), cs2, cs3, cs4)
+	prevotes := signVotes(types.VoteTypePrevote, propBlock.Hash(), propBlock.MakePartSet(partSize).Header(), vs2, vs3, vs4)
 
 	// before we time out into new round, set next proposer
 	// and next proposal block
@@ -709,13 +735,13 @@ func TestLockPOLSafety1(t *testing.T) {
 	log.Warn("old prop", "hash", fmt.Sprintf("%X", propBlock.Hash()))
 
 	// we do see them precommit nil
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, types.PartSetHeader{}, nil, cs2, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrecommit, nil, types.PartSetHeader{}, vs2, vs3, vs4)
 
-	prop, propBlock := decideProposal(cs1, cs2, cs2.Height, cs2.Round+1)
+	prop, propBlock := decideProposal(cs1, vs2, vs2.Height, vs2.Round+1)
 	propBlockHash := propBlock.Hash()
-	propBlockParts := propBlock.MakePartSet()
+	propBlockParts := propBlock.MakePartSet(partSize)
 
-	incrementRound(cs2, cs3, cs4)
+	incrementRound(vs2, vs3, vs4)
 
 	//XXX: this isnt gauranteed to get there before the timeoutPropose ...
 	cs1.SetProposalAndBlock(prop, propBlock, propBlockParts, "some peer")
@@ -746,18 +772,18 @@ func TestLockPOLSafety1(t *testing.T) {
 	validatePrevote(t, cs1, 1, vss[0], propBlockHash)
 
 	// now we see the others prevote for it, so we should lock on it
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, propBlockHash, propBlockParts.Header(), nil, cs2, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrevote, propBlockHash, propBlockParts.Header(), vs2, vs3, vs4)
 
 	<-voteCh // precommit
 
 	// we should have precommitted
 	validatePrecommit(t, cs1, 1, 1, vss[0], propBlockHash, propBlockHash)
 
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, types.PartSetHeader{}, nil, cs2, cs3)
+	signAddVotes(cs1, types.VoteTypePrecommit, nil, types.PartSetHeader{}, vs2, vs3)
 
 	<-timeoutWaitCh
 
-	incrementRound(cs2, cs3, cs4)
+	incrementRound(vs2, vs3, vs4)
 
 	<-newRoundCh
 
@@ -778,7 +804,7 @@ func TestLockPOLSafety1(t *testing.T) {
 	newStepCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewRoundStep(), 1)
 
 	// add prevotes from the earlier round
-	addVoteToFromMany(cs1, prevotes, cs2, cs3, cs4)
+	addVotes(cs1, prevotes...)
 
 	log.Warn("Done adding prevotes!")
 
@@ -794,30 +820,33 @@ func TestLockPOLSafety1(t *testing.T) {
 // dont see P0, lock on P1 at R1, dont unlock using P0 at R2
 func TestLockPOLSafety2(t *testing.T) {
 	cs1, vss := randConsensusState(4)
-	cs2, cs3, cs4 := vss[1], vss[2], vss[3]
+	vs2, vs3, vs4 := vss[1], vss[2], vss[3]
+
+	partSize := config.GetInt("block_part_size")
 
 	proposalCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringCompleteProposal(), 1)
 	timeoutProposeCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutPropose(), 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutWait(), 1)
 	newRoundCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewRound(), 1)
 	unlockCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringUnlock(), 1)
-	voteCh := subscribeToVoter(cs1, cs1.privValidator.Address)
+	voteCh := subscribeToVoter(cs1, cs1.privValidator.GetAddress())
 
 	// the block for R0: gets polkad but we miss it
 	// (even though we signed it, shhh)
 	_, propBlock0 := decideProposal(cs1, vss[0], cs1.Height, cs1.Round)
 	propBlockHash0 := propBlock0.Hash()
-	propBlockParts0 := propBlock0.MakePartSet()
+	propBlockParts0 := propBlock0.MakePartSet(partSize)
 
 	// the others sign a polka but we don't see it
-	prevotes := signVoteMany(types.VoteTypePrevote, propBlockHash0, propBlockParts0.Header(), cs2, cs3, cs4)
+	prevotes := signVotes(types.VoteTypePrevote, propBlockHash0, propBlockParts0.Header(), vs2, vs3, vs4)
 
 	// the block for round 1
-	prop1, propBlock1 := decideProposal(cs1, cs2, cs2.Height, cs2.Round+1)
+	prop1, propBlock1 := decideProposal(cs1, vs2, vs2.Height, vs2.Round+1)
 	propBlockHash1 := propBlock1.Hash()
-	propBlockParts1 := propBlock1.MakePartSet()
+	propBlockParts1 := propBlock1.MakePartSet(partSize)
+	propBlockID1 := types.BlockID{propBlockHash1, propBlockParts1.Header()}
 
-	incrementRound(cs2, cs3, cs4)
+	incrementRound(vs2, vs3, vs4)
 
 	cs1.updateRoundStep(0, RoundStepPrecommitWait)
 
@@ -832,28 +861,30 @@ func TestLockPOLSafety2(t *testing.T) {
 
 	<-voteCh // prevote
 
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, propBlockHash1, propBlockParts1.Header(), nil, cs2, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrevote, propBlockHash1, propBlockParts1.Header(), vs2, vs3, vs4)
 
 	<-voteCh // precommit
 	// the proposed block should now be locked and our precommit added
 	validatePrecommit(t, cs1, 1, 1, vss[0], propBlockHash1, propBlockHash1)
 
 	// add precommits from the rest
-	signAddVoteToFromMany(types.VoteTypePrecommit, cs1, nil, types.PartSetHeader{}, nil, cs2, cs4)
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs3, propBlockHash1, propBlockParts1.Header(), nil)
+	signAddVotes(cs1, types.VoteTypePrecommit, nil, types.PartSetHeader{}, vs2, vs4)
+	signAddVotes(cs1, types.VoteTypePrecommit, propBlockHash1, propBlockParts1.Header(), vs3)
 
-	incrementRound(cs2, cs3, cs4)
+	incrementRound(vs2, vs3, vs4)
 
 	// timeout of precommit wait to new round
 	<-timeoutWaitCh
 
 	// in round 2 we see the polkad block from round 0
-	newProp := types.NewProposal(height, 2, propBlockParts0.Header(), 0)
-	if err := cs3.SignProposal(config.GetString("chain_id"), newProp); err != nil {
-		panic(err)
+	newProp := types.NewProposal(height, 2, propBlockParts0.Header(), 0, propBlockID1)
+	if err := vs3.SignProposal(config.GetString("chain_id"), newProp); err != nil {
+		t.Fatal(err)
 	}
 	cs1.SetProposalAndBlock(newProp, propBlock0, propBlockParts0, "some peer")
-	addVoteToFromMany(cs1, prevotes, cs2, cs3, cs4) // add the pol votes
+
+	// Add the pol votes
+	addVotes(cs1, prevotes...)
 
 	<-newRoundCh
 	log.Notice("### ONTO Round 2")
@@ -884,13 +915,13 @@ func TestLockPOLSafety2(t *testing.T) {
 /*
 func TestSlashingPrevotes(t *testing.T) {
 	cs1, vss := randConsensusState(2)
-	cs2 := vss[1]
+	vs2 := vss[1]
 
 
 	proposalCh := subscribeToEvent(cs1.evsw,"tester",types.EventStringCompleteProposal() , 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw,"tester",types.EventStringTimeoutWait() , 1)
 	newRoundCh := subscribeToEvent(cs1.evsw,"tester",types.EventStringNewRound() , 1)
-	voteCh := subscribeToVoter(cs1, cs1.privValidator.Address)
+	voteCh := subscribeToVoter(cs1, cs1.privValidator.GetAddress())
 
 	// start round and wait for propose and prevote
 	startTestRound(cs1, cs1.Height, 0)
@@ -904,7 +935,7 @@ func TestSlashingPrevotes(t *testing.T) {
 	// add one for a different block should cause us to go into prevote wait
 	hash := rs.ProposalBlock.Hash()
 	hash[0] = byte(hash[0]+1) % 255
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, hash, rs.ProposalBlockParts.Header(), nil)
+	signAddVotes(cs1, types.VoteTypePrevote, hash, rs.ProposalBlockParts.Header(), vs2)
 
 	<-timeoutWaitCh
 
@@ -912,20 +943,20 @@ func TestSlashingPrevotes(t *testing.T) {
 	// away and ignore more prevotes (and thus fail to slash!)
 
 	// add the conflicting vote
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(),nil)
+	signAddVotes(cs1, types.VoteTypePrevote, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), vs2)
 
 	// XXX: Check for existence of Dupeout info
 }
 
 func TestSlashingPrecommits(t *testing.T) {
 	cs1, vss := randConsensusState(2)
-	cs2 := vss[1]
+	vs2 := vss[1]
 
 
 	proposalCh := subscribeToEvent(cs1.evsw,"tester",types.EventStringCompleteProposal() , 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw,"tester",types.EventStringTimeoutWait() , 1)
 	newRoundCh := subscribeToEvent(cs1.evsw,"tester",types.EventStringNewRound() , 1)
-	voteCh := subscribeToVoter(cs1, cs1.privValidator.Address)
+	voteCh := subscribeToVoter(cs1, cs1.privValidator.GetAddress())
 
 	// start round and wait for propose and prevote
 	startTestRound(cs1, cs1.Height, 0)
@@ -933,8 +964,8 @@ func TestSlashingPrecommits(t *testing.T) {
 	re := <-proposalCh
 	<-voteCh // prevote
 
-	// add prevote from cs2
-	signAddVoteToFrom(types.VoteTypePrevote, cs1, cs2, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), nil)
+	// add prevote from vs2
+	signAddVotes(cs1, types.VoteTypePrevote, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), vs2)
 
 	<-voteCh // precommit
 
@@ -942,13 +973,13 @@ func TestSlashingPrecommits(t *testing.T) {
 	// add one for a different block should cause us to go into prevote wait
 	hash := rs.ProposalBlock.Hash()
 	hash[0] = byte(hash[0]+1) % 255
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, hash, rs.ProposalBlockParts.Header(),nil)
+	signAddVotes(cs1, types.VoteTypePrecommit, hash, rs.ProposalBlockParts.Header(), vs2)
 
 	// NOTE: we have to send the vote for different block first so we don't just go into precommit round right
 	// away and ignore more prevotes (and thus fail to slash!)
 
-	// add precommit from cs2
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(),nil)
+	// add precommit from vs2
+	signAddVotes(cs1, types.VoteTypePrecommit, rs.ProposalBlock.Hash(), rs.ProposalBlockParts.Header(), vs2)
 
 	// XXX: Check for existence of Dupeout info
 }
@@ -964,13 +995,15 @@ func TestSlashingPrecommits(t *testing.T) {
 // we receive a final precommit after going into next round, but others might have gone to commit already!
 func TestHalt1(t *testing.T) {
 	cs1, vss := randConsensusState(4)
-	cs2, cs3, cs4 := vss[1], vss[2], vss[3]
+	vs2, vs3, vs4 := vss[1], vss[2], vss[3]
+
+	partSize := config.GetInt("block_part_size")
 
 	proposalCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringCompleteProposal(), 1)
 	timeoutWaitCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringTimeoutWait(), 1)
 	newRoundCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewRound(), 1)
 	newBlockCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewBlock(), 1)
-	voteCh := subscribeToVoter(cs1, cs1.privValidator.Address)
+	voteCh := subscribeToVoter(cs1, cs1.privValidator.GetAddress())
 
 	// start round and wait for propose and prevote
 	startTestRound(cs1, cs1.Height, 0)
@@ -978,23 +1011,23 @@ func TestHalt1(t *testing.T) {
 	re := <-proposalCh
 	rs := re.(types.EventDataRoundState).RoundState.(*RoundState)
 	propBlock := rs.ProposalBlock
-	propBlockParts := propBlock.MakePartSet()
+	propBlockParts := propBlock.MakePartSet(partSize)
 
 	<-voteCh // prevote
 
-	signAddVoteToFromMany(types.VoteTypePrevote, cs1, propBlock.Hash(), propBlockParts.Header(), nil, cs3, cs4)
+	signAddVotes(cs1, types.VoteTypePrevote, propBlock.Hash(), propBlockParts.Header(), vs3, vs4)
 	<-voteCh // precommit
 
 	// the proposed block should now be locked and our precommit added
 	validatePrecommit(t, cs1, 0, 0, vss[0], propBlock.Hash(), propBlock.Hash())
 
 	// add precommits from the rest
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs2, nil, types.PartSetHeader{}, nil) // didnt receive proposal
-	signAddVoteToFrom(types.VoteTypePrecommit, cs1, cs3, propBlock.Hash(), propBlockParts.Header(), nil)
-	// we receive this later, but cs3 might receive it earlier and with ours will go to commit!
-	precommit4 := signVote(cs4, types.VoteTypePrecommit, propBlock.Hash(), propBlockParts.Header())
+	signAddVotes(cs1, types.VoteTypePrecommit, nil, types.PartSetHeader{}, vs2) // didnt receive proposal
+	signAddVotes(cs1, types.VoteTypePrecommit, propBlock.Hash(), propBlockParts.Header(), vs3)
+	// we receive this later, but vs3 might receive it earlier and with ours will go to commit!
+	precommit4 := signVote(vs4, types.VoteTypePrecommit, propBlock.Hash(), propBlockParts.Header())
 
-	incrementRound(cs2, cs3, cs4)
+	incrementRound(vs2, vs3, vs4)
 
 	// timeout to new round
 	<-timeoutWaitCh
@@ -1012,7 +1045,7 @@ func TestHalt1(t *testing.T) {
 	validatePrevote(t, cs1, 0, vss[0], rs.LockedBlock.Hash())
 
 	// now we receive the precommit from the previous round
-	addVoteToFrom(cs1, cs4, precommit4)
+	addVotes(cs1, precommit4)
 
 	// receiving that precommit should take us straight to commit
 	<-newBlockCh
diff --git a/consensus/test_data/README.md b/consensus/test_data/README.md
index 8d14b8e6..8e299d4f 100644
--- a/consensus/test_data/README.md
+++ b/consensus/test_data/README.md
@@ -1,7 +1,18 @@
 # Generating test data
 
+TODO: automate this process.
+
 The easiest way to generate this data is to copy `~/.tendermint_test/somedir/*` to `~/.tendermint`
-and to run a local node.
+and to run a local node. Note the tests expect a wal for block 1.
+
+For `empty_block.cswal`, run the node and don't send any transactions.
+
+For `small_block1.cswal` and `small_block2.cswal`,
+use the `scripts/txs/random.sh 1000 36657` to start sending transactions before starting the node.
+`small_block1.cswal` uses the default large block part size, so the block should have one big part.
+For `small_block2.cswal`, set `block_part_size = 512` in the config.toml.
+
+Make sure to adjust the stepChanges in the testCases if the number of messages changes
 
 If you need to change the signatures, you can use a script as follows:
 The privBytes comes from `config/tendermint_test/...`:
diff --git a/consensus/test_data/empty_block.cswal b/consensus/test_data/empty_block.cswal
index 29361c53..b2e1a296 100644
--- a/consensus/test_data/empty_block.cswal
+++ b/consensus/test_data/empty_block.cswal
@@ -1,9 +1,10 @@
 #HEIGHT: 1
-{"time":"2016-04-03T11:23:54.387Z","msg":[3,{"duration":972835254,"height":1,"round":0,"step":1}]}
-{"time":"2016-04-03T11:23:54.388Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPropose"}]}
-{"time":"2016-04-03T11:23:54.388Z","msg":[2,{"msg":[17,{"Proposal":{"height":1,"round":0,"block_parts_header":{"total":1,"hash":"3BA1E90CB868DA6B4FD7F3589826EC461E9EB4EF"},"pol_round":-1,"signature":"3A2ECD5023B21EC144EC16CFF1B992A4321317B83EEDD8969FDFEA6EB7BF4389F38DDA3E7BB109D63A07491C16277A197B241CF1F05F5E485C59882ECACD9E07"}}],"peer_key":""}]}
-{"time":"2016-04-03T11:23:54.389Z","msg":[2,{"msg":[19,{"Height":1,"Round":0,"Part":{"index":0,"bytes":"0101010F74656E6465726D696E745F7465737401011441D59F4B718AC00000000000000114C4B01D3810579550997AC5641E759E20D99B51C10001000100","proof":{"aunts":[]}}}],"peer_key":""}]}
-{"time":"2016-04-03T11:23:54.390Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPrevote"}]}
-{"time":"2016-04-03T11:23:54.390Z","msg":[2,{"msg":[20,{"ValidatorIndex":0,"Vote":{"height":1,"round":0,"type":1,"block_hash":"4291966B8A9DFBA00AEC7C700F2718E61DF4331D","block_parts_header":{"total":1,"hash":"3BA1E90CB868DA6B4FD7F3589826EC461E9EB4EF"},"signature":"47D2A75A4E2F15DB1F0D1B656AC0637AF9AADDFEB6A156874F6553C73895E5D5DC948DBAEF15E61276C5342D0E638DFCB77C971CD282096EA8735A564A90F008"}}],"peer_key":""}]}
-{"time":"2016-04-03T11:23:54.392Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPrecommit"}]}
-{"time":"2016-04-03T11:23:54.392Z","msg":[2,{"msg":[20,{"ValidatorIndex":0,"Vote":{"height":1,"round":0,"type":2,"block_hash":"4291966B8A9DFBA00AEC7C700F2718E61DF4331D","block_parts_header":{"total":1,"hash":"3BA1E90CB868DA6B4FD7F3589826EC461E9EB4EF"},"signature":"39147DA595F08B73CF8C899967C8403B5872FD9042FFA4E239159E0B6C5D9665C9CA81D766EACA2AE658872F94C2FCD1E34BF51859CD5B274DA8512BACE4B50D"}}],"peer_key":""}]}
+{"time":"2016-11-16T03:26:47.819Z","msg":[3,{"duration":966969466,"height":1,"round":0,"step":1}]}
+{"time":"2016-11-16T03:26:47.822Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPropose"}]}
+{"time":"2016-11-16T03:26:47.822Z","msg":[2,{"msg":[17,{"Proposal":{"height":1,"round":0,"block_parts_header":{"total":1,"hash":"2AF632C1AFEE1FC06B297A5E5D45171FE1C79B24"},"pol_round":-1,"pol_block_id":{"hash":"","parts":{"total":0,"hash":""}},"signature":"C5C9290F723CFF1E9EB1D7A493FF0CAAEE2E3F1865EA4014BEEECC4682CDEF24C73C07A725A273B20340A1F49C4E055CAC4B349281727096235E3C7F72DA3C00"}}],"peer_key":""}]}
+{"time":"2016-11-16T03:26:47.823Z","msg":[2,{"msg":[19,{"Height":1,"Round":0,"Part":{"index":0,"bytes":"0101010F74656E6465726D696E745F7465737401011487695300231B000000000000000114C4B01D3810579550997AC5641E759E20D99B51C10001000100000000","proof":{"aunts":[]}}}],"peer_key":""}]}
+{"time":"2016-11-16T03:26:47.825Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPrevote"}]}
+{"time":"2016-11-16T03:26:47.825Z","msg":[2,{"msg":[20,{"Vote":{"validator_address":"D028C9981F7A87F3093672BF0D5B0E2A1B3ED456","validator_index":0,"height":1,"round":0,"type":1,"block_id":{"hash":"B6CD5337C4585262B851F75F0532EA4E5B12D92C","parts":{"total":1,"hash":"2AF632C1AFEE1FC06B297A5E5D45171FE1C79B24"}},"signature":"7D52D42FBEA806740547AEFBCA5BF30AB758C320307E7C48C39A9DC3C027EE87F10808B532F7EF168BC170649A8330C194FE9E45F84C0F74DAC508D380CCA808"}}],"peer_key":""}]}
+{"time":"2016-11-16T03:26:47.825Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPrecommit"}]}
+{"time":"2016-11-16T03:26:47.825Z","msg":[2,{"msg":[20,{"Vote":{"validator_address":"D028C9981F7A87F3093672BF0D5B0E2A1B3ED456","validator_index":0,"height":1,"round":0,"type":2,"block_id":{"hash":"B6CD5337C4585262B851F75F0532EA4E5B12D92C","parts":{"total":1,"hash":"2AF632C1AFEE1FC06B297A5E5D45171FE1C79B24"}},"signature":"450DFB9AA3CDE45B5081A95C488DB7785EE0A6875898662ADDB289FB0A3D7BA5C69E6369272A5F285EBE1B87A4D55C23F1D45EA924E3562FE0C569E44C499504"}}],"peer_key":""}]}
+{"time":"2016-11-16T03:26:47.826Z","msg":[1,{"height":1,"round":0,"step":"RoundStepCommit"}]}
diff --git a/consensus/test_data/small_block1.cswal b/consensus/test_data/small_block1.cswal
index 232bf20f..c027e437 100644
--- a/consensus/test_data/small_block1.cswal
+++ b/consensus/test_data/small_block1.cswal
@@ -1,9 +1,10 @@
 #HEIGHT: 1
-{"time":"2016-10-11T15:29:08.113Z","msg":[3,{"duration":0,"height":1,"round":0,"step":1}]}
-{"time":"2016-10-11T15:29:08.115Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPropose"}]}
-{"time":"2016-10-11T15:29:08.115Z","msg":[2,{"msg":[17,{"Proposal":{"height":1,"round":0,"block_parts_header":{"total":1,"hash":"A2C0B5D384DFF2692FF679D00CEAE93A55DCDD1A"},"pol_round":-1,"signature":"116961B715FB54C09983209F7F3BFD95C7DA2E0D7AB9CFE9F0750F2402E2AEB715CFD55FB2C5DB88F485391D426A48705E0474AB94328463290D086D88BAD704"}}],"peer_key":""}]}
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diff --git a/consensus/test_data/small_block2.cswal b/consensus/test_data/small_block2.cswal
index 84d86022..54279a3b 100644
--- a/consensus/test_data/small_block2.cswal
+++ b/consensus/test_data/small_block2.cswal
@@ -1,11 +1,14 @@
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-{"time":"2016-10-11T16:21:23.447Z","msg":[2,{"msg":[20,{"ValidatorIndex":0,"Vote":{"height":1,"round":0,"type":1,"block_hash":"AAE0ECF64D818A61F6E3D6D11E60F343C3FC8800","block_parts_header":{"total":3,"hash":"88BC082C86DED0A5E2BBC3677B610D155FEDBCEA"},"signature":"0870A9C3FF59DE0F5574B77F030BD160C1E2966AECE815E7C97CFA8BC4A6B01D7A10D91416B1AA02D49EFF7F08A239048CD9CD93E7AE4F80871FBFFF7DBFC50C"}}],"peer_key":""}]}
-{"time":"2016-10-11T16:21:23.448Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPrecommit"}]}
-{"time":"2016-10-11T16:21:23.448Z","msg":[2,{"msg":[20,{"ValidatorIndex":0,"Vote":{"height":1,"round":0,"type":2,"block_hash":"AAE0ECF64D818A61F6E3D6D11E60F343C3FC8800","block_parts_header":{"total":3,"hash":"88BC082C86DED0A5E2BBC3677B610D155FEDBCEA"},"signature":"0CEEA8A987D88D0A0870C0076DB8D1B57D3B051D017745B46C4710BBE6DF0F9AE8D5A95B49E4158A1A8C8C6475B8A8E91275303B9C10A5C0C18F40EBB0DA0905"}}],"peer_key":""}]}
+{"time":"2016-11-16T05:41:35.271Z","msg":[3,{"duration":953420437,"height":1,"round":0,"step":1}]}
+{"time":"2016-11-16T05:41:35.272Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPropose"}]}
+{"time":"2016-11-16T05:41:35.272Z","msg":[2,{"msg":[17,{"Proposal":{"height":1,"round":0,"block_parts_header":{"total":5,"hash":"2BDB8E53CD09D48FF4CB53E538EE4824D1F66AF6"},"pol_round":-1,"pol_block_id":{"hash":"","parts":{"total":0,"hash":""}},"signature":"96B4688C79E9DEB99BCFD86D663FB206FEF8793A29815474B45090D3D7D2955EC9E19A0750BCE9F84C2331F566E3D8073DFA2ECB387C266E502CA3BED12D4407"}}],"peer_key":""}]}
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+{"time":"2016-11-16T05:41:35.272Z","msg":[2,{"msg":[19,{"Height":1,"Round":0,"Part":{"index":4,"bytes":"64636261353030010F616263643530313D64636261353031010F616263643530323D64636261353032010F616263643530333D64636261353033010F616263643530343D64636261353034010F616263643530353D64636261353035010F616263643530363D64636261353036010F616263643530373D64636261353037010F616263643530383D64636261353038010F616263643530393D64636261353039010F616263643531303D64636261353130010F616263643531313D64636261353131010F616263643531323D646362613531320100000000","proof":{"aunts":["8AA5C39BFC1E062439B4FC6B03812909E4D9D85C","E9C0EE8407389C3CBF707425A577513095F38DE2"]}}}],"peer_key":""}]}
+{"time":"2016-11-16T05:41:35.273Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPrevote"}]}
+{"time":"2016-11-16T05:41:35.273Z","msg":[2,{"msg":[20,{"Vote":{"validator_address":"D028C9981F7A87F3093672BF0D5B0E2A1B3ED456","validator_index":0,"height":1,"round":0,"type":1,"block_id":{"hash":"06C99E8836006B39E00C84828A87920E0354CC95","parts":{"total":5,"hash":"2BDB8E53CD09D48FF4CB53E538EE4824D1F66AF6"}},"signature":"7FD916E1CC78500981F05A936E9099A7500408F2A786DFB1ACAADA7754E014CF53B87216A8AE1DF9A876C51CD5F3EF57CA04E1EEFC21085EF57FA9F7BE32230F"}}],"peer_key":""}]}
+{"time":"2016-11-16T05:41:35.303Z","msg":[1,{"height":1,"round":0,"step":"RoundStepPrecommit"}]}
+{"time":"2016-11-16T05:41:35.303Z","msg":[2,{"msg":[20,{"Vote":{"validator_address":"D028C9981F7A87F3093672BF0D5B0E2A1B3ED456","validator_index":0,"height":1,"round":0,"type":2,"block_id":{"hash":"06C99E8836006B39E00C84828A87920E0354CC95","parts":{"total":5,"hash":"2BDB8E53CD09D48FF4CB53E538EE4824D1F66AF6"}},"signature":"BB4EC9F1FD4DA983C1756499DA94947E8CA8C1DD882F84C369C672FB8542C5722311787B9E774F4F1776CC4B46A25D369F7FCB8D5D34BB73E85C2CF94852DF0B"}}],"peer_key":""}]}
+{"time":"2016-11-16T05:41:35.303Z","msg":[1,{"height":1,"round":0,"step":"RoundStepCommit"}]}
diff --git a/consensus/wal.go b/consensus/wal.go
index 8460a832..2bd24c72 100644
--- a/consensus/wal.go
+++ b/consensus/wal.go
@@ -54,7 +54,19 @@ func NewWAL(walDir string, light bool) (*WAL, error) {
 		light: light,
 	}
 	wal.BaseService = *NewBaseService(log, "WAL", wal)
-	return wal, nil
+	_, err = wal.Start()
+	return wal, err
+}
+
+func (wal *WAL) OnStart() error {
+	wal.BaseService.OnStart()
+	size, err := wal.group.Head.Size()
+	if err != nil {
+		return err
+	} else if size == 0 {
+		wal.writeHeight(1)
+	}
+	return nil
 }
 
 func (wal *WAL) OnStop() {
@@ -80,7 +92,7 @@ func (wal *WAL) Save(wmsg WALMessage) {
 	// Write #HEIGHT: XYZ if new height
 	if edrs, ok := wmsg.(types.EventDataRoundState); ok {
 		if edrs.Step == RoundStepNewHeight.String() {
-			wal.group.WriteLine(Fmt("#HEIGHT: %v", edrs.Height))
+			wal.writeHeight(edrs.Height)
 		}
 	}
 	// Write the wal message
@@ -90,3 +102,7 @@ func (wal *WAL) Save(wmsg WALMessage) {
 		PanicQ(Fmt("Error writing msg to consensus wal. Error: %v \n\nMessage: %v", err, wmsg))
 	}
 }
+
+func (wal *WAL) writeHeight(height int) {
+	wal.group.WriteLine(Fmt("#HEIGHT: %v", height))
+}
diff --git a/node/node.go b/node/node.go
index 7c4a08e3..45e7ae00 100644
--- a/node/node.go
+++ b/node/node.go
@@ -94,7 +94,7 @@ func NewNode(config cfg.Config, privValidator *types.PrivValidator, clientCreato
 	}
 
 	// Make BlockchainReactor
-	bcReactor := bc.NewBlockchainReactor(state.Copy(), proxyApp.Consensus(), blockStore, fastSync)
+	bcReactor := bc.NewBlockchainReactor(config, state.Copy(), proxyApp.Consensus(), blockStore, fastSync)
 
 	// Make MempoolReactor
 	mempool := mempl.NewMempool(config, proxyApp.Mempool())
@@ -102,7 +102,7 @@ func NewNode(config cfg.Config, privValidator *types.PrivValidator, clientCreato
 
 	// Make ConsensusReactor
 	consensusState := consensus.NewConsensusState(config, state.Copy(), proxyApp.Consensus(), blockStore, mempool)
-	consensusReactor := consensus.NewConsensusReactor(consensusState, blockStore, fastSync)
+	consensusReactor := consensus.NewConsensusReactor(consensusState, fastSync)
 	if privValidator != nil {
 		consensusReactor.SetPrivValidator(privValidator)
 	}
diff --git a/scripts/txs/random.sh b/scripts/txs/random.sh
new file mode 100644
index 00000000..742d981c
--- /dev/null
+++ b/scripts/txs/random.sh
@@ -0,0 +1,19 @@
+#! /bin/bash
+set -u
+
+function toHex() {
+	echo -n $1 | hexdump -ve '1/1 "%.2X"'
+}
+
+N=$1
+PORT=$2
+
+for i in `seq 1 $N`; do
+	# store key value pair
+	KEY="abcd$i"
+	VALUE="dcba$i"
+	echo "$KEY:$VALUE"
+	curl 127.0.0.1:$PORT/broadcast_tx_sync?tx=\"$(toHex $KEY=$VALUE)\"
+done
+
+
diff --git a/state/execution.go b/state/execution.go
index b6bc215e..e5653e7e 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -43,8 +43,7 @@ func (s *State) ExecBlock(eventCache types.Fireable, proxyAppConn proxy.AppConnC
 	// All good!
 	nextValSet.IncrementAccum(1)
 	s.LastBlockHeight = block.Height
-	s.LastBlockHash = block.Hash()
-	s.LastBlockParts = blockPartsHeader
+	s.LastBlockID = types.BlockID{block.Hash(), blockPartsHeader}
 	s.LastBlockTime = block.Time
 	s.Validators = nextValSet
 	s.LastValidators = valSet
@@ -119,7 +118,7 @@ func (s *State) execBlockOnProxyApp(eventCache types.Fireable, proxyAppConn prox
 
 func (s *State) validateBlock(block *types.Block) error {
 	// Basic block validation.
-	err := block.ValidateBasic(s.ChainID, s.LastBlockHeight, s.LastBlockHash, s.LastBlockParts, s.LastBlockTime, s.AppHash)
+	err := block.ValidateBasic(s.ChainID, s.LastBlockHeight, s.LastBlockID, s.LastBlockTime, s.AppHash)
 	if err != nil {
 		return err
 	}
@@ -135,7 +134,7 @@ func (s *State) validateBlock(block *types.Block) error {
 				s.LastValidators.Size(), len(block.LastCommit.Precommits))
 		}
 		err := s.LastValidators.VerifyCommit(
-			s.ChainID, s.LastBlockHash, s.LastBlockParts, block.Height-1, block.LastCommit)
+			s.ChainID, s.LastBlockID, block.Height-1, block.LastCommit)
 		if err != nil {
 			return err
 		}
diff --git a/state/state.go b/state/state.go
index 798e8ce7..21348486 100644
--- a/state/state.go
+++ b/state/state.go
@@ -25,8 +25,7 @@ type State struct {
 	GenesisDoc      *types.GenesisDoc
 	ChainID         string
 	LastBlockHeight int // Genesis state has this set to 0.  So, Block(H=0) does not exist.
-	LastBlockHash   []byte
-	LastBlockParts  types.PartSetHeader
+	LastBlockID     types.BlockID
 	LastBlockTime   time.Time
 	Validators      *types.ValidatorSet
 	LastValidators  *types.ValidatorSet
@@ -56,8 +55,7 @@ func (s *State) Copy() *State {
 		GenesisDoc:      s.GenesisDoc,
 		ChainID:         s.ChainID,
 		LastBlockHeight: s.LastBlockHeight,
-		LastBlockHash:   s.LastBlockHash,
-		LastBlockParts:  s.LastBlockParts,
+		LastBlockID:     s.LastBlockID,
 		LastBlockTime:   s.LastBlockTime,
 		Validators:      s.Validators.Copy(),
 		LastValidators:  s.LastValidators.Copy(),
@@ -117,8 +115,7 @@ func MakeGenesisState(db dbm.DB, genDoc *types.GenesisDoc) *State {
 		GenesisDoc:      genDoc,
 		ChainID:         genDoc.ChainID,
 		LastBlockHeight: 0,
-		LastBlockHash:   nil,
-		LastBlockParts:  types.PartSetHeader{},
+		LastBlockID:     types.BlockID{},
 		LastBlockTime:   genDoc.GenesisTime,
 		Validators:      types.NewValidatorSet(validators),
 		LastValidators:  types.NewValidatorSet(nil),
diff --git a/types/block.go b/types/block.go
index a6f7bb5f..bf6ec2b2 100644
--- a/types/block.go
+++ b/types/block.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"strings"
 	"time"
 
@@ -21,8 +22,8 @@ type Block struct {
 }
 
 // Basic validation that doesn't involve state data.
-func (b *Block) ValidateBasic(chainID string, lastBlockHeight int, lastBlockHash []byte,
-	lastBlockParts PartSetHeader, lastBlockTime time.Time, appHash []byte) error {
+func (b *Block) ValidateBasic(chainID string, lastBlockHeight int, lastBlockID BlockID,
+	lastBlockTime time.Time, appHash []byte) error {
 	if b.ChainID != chainID {
 		return errors.New(Fmt("Wrong Block.Header.ChainID. Expected %v, got %v", chainID, b.ChainID))
 	}
@@ -39,11 +40,8 @@ func (b *Block) ValidateBasic(chainID string, lastBlockHeight int, lastBlockHash
 	if b.NumTxs != len(b.Data.Txs) {
 		return errors.New(Fmt("Wrong Block.Header.NumTxs. Expected %v, got %v", len(b.Data.Txs), b.NumTxs))
 	}
-	if !bytes.Equal(b.LastBlockHash, lastBlockHash) {
-		return errors.New(Fmt("Wrong Block.Header.LastBlockHash.  Expected %X, got %X", lastBlockHash, b.LastBlockHash))
-	}
-	if !b.LastBlockParts.Equals(lastBlockParts) {
-		return errors.New(Fmt("Wrong Block.Header.LastBlockParts. Expected %v, got %v", lastBlockParts, b.LastBlockParts))
+	if !b.LastBlockID.Equals(lastBlockID) {
+		return errors.New(Fmt("Wrong Block.Header.LastBlockID.  Expected %v, got %v", lastBlockID, b.LastBlockID))
 	}
 	if !bytes.Equal(b.LastCommitHash, b.LastCommit.Hash()) {
 		return errors.New(Fmt("Wrong Block.Header.LastCommitHash.  Expected %X, got %X", b.LastCommitHash, b.LastCommit.Hash()))
@@ -83,8 +81,8 @@ func (b *Block) Hash() []byte {
 	return b.Header.Hash()
 }
 
-func (b *Block) MakePartSet() *PartSet {
-	return NewPartSetFromData(wire.BinaryBytes(b))
+func (b *Block) MakePartSet(partSize int) *PartSet {
+	return NewPartSetFromData(wire.BinaryBytes(b), partSize)
 }
 
 // Convenience.
@@ -130,16 +128,15 @@ func (b *Block) StringShort() string {
 //-----------------------------------------------------------------------------
 
 type Header struct {
-	ChainID        string        `json:"chain_id"`
-	Height         int           `json:"height"`
-	Time           time.Time     `json:"time"`
-	NumTxs         int           `json:"num_txs"`
-	LastBlockHash  []byte        `json:"last_block_hash"`
-	LastBlockParts PartSetHeader `json:"last_block_parts"`
-	LastCommitHash []byte        `json:"last_commit_hash"`
-	DataHash       []byte        `json:"data_hash"`
-	ValidatorsHash []byte        `json:"validators_hash"`
-	AppHash        []byte        `json:"app_hash"` // state merkle root of txs from the previous block
+	ChainID        string    `json:"chain_id"`
+	Height         int       `json:"height"`
+	Time           time.Time `json:"time"`
+	NumTxs         int       `json:"num_txs"`
+	LastBlockID    BlockID   `json:"last_block_id"`
+	LastCommitHash []byte    `json:"last_commit_hash"`
+	DataHash       []byte    `json:"data_hash"`
+	ValidatorsHash []byte    `json:"validators_hash"`
+	AppHash        []byte    `json:"app_hash"` // state merkle root of txs from the previous block
 }
 
 // NOTE: hash is nil if required fields are missing.
@@ -148,16 +145,15 @@ func (h *Header) Hash() []byte {
 		return nil
 	}
 	return merkle.SimpleHashFromMap(map[string]interface{}{
-		"ChainID":        h.ChainID,
-		"Height":         h.Height,
-		"Time":           h.Time,
-		"NumTxs":         h.NumTxs,
-		"LastBlock":      h.LastBlockHash,
-		"LastBlockParts": h.LastBlockParts,
-		"LastCommit":     h.LastCommitHash,
-		"Data":           h.DataHash,
-		"Validators":     h.ValidatorsHash,
-		"App":            h.AppHash,
+		"ChainID":     h.ChainID,
+		"Height":      h.Height,
+		"Time":        h.Time,
+		"NumTxs":      h.NumTxs,
+		"LastBlockID": h.LastBlockID,
+		"LastCommit":  h.LastCommitHash,
+		"Data":        h.DataHash,
+		"Validators":  h.ValidatorsHash,
+		"App":         h.AppHash,
 	})
 }
 
@@ -170,8 +166,7 @@ func (h *Header) StringIndented(indent string) string {
 %s  Height:         %v
 %s  Time:           %v
 %s  NumTxs:         %v
-%s  LastBlock:      %X
-%s  LastBlockParts: %v
+%s  LastBlockID:    %v
 %s  LastCommit:     %X
 %s  Data:           %X
 %s  Validators:     %X
@@ -181,8 +176,7 @@ func (h *Header) StringIndented(indent string) string {
 		indent, h.Height,
 		indent, h.Time,
 		indent, h.NumTxs,
-		indent, h.LastBlockHash,
-		indent, h.LastBlockParts,
+		indent, h.LastBlockID,
 		indent, h.LastCommitHash,
 		indent, h.DataHash,
 		indent, h.ValidatorsHash,
@@ -197,6 +191,7 @@ type Commit struct {
 	// NOTE: The Precommits are in order of address to preserve the bonded ValidatorSet order.
 	// Any peer with a block can gossip precommits by index with a peer without recalculating the
 	// active ValidatorSet.
+	BlockID    BlockID `json:"blockID"`
 	Precommits []*Vote `json:"precommits"`
 
 	// Volatile
@@ -268,6 +263,9 @@ func (commit *Commit) IsCommit() bool {
 }
 
 func (commit *Commit) ValidateBasic() error {
+	if commit.BlockID.IsZero() {
+		return errors.New("Commit cannot be for nil block")
+	}
 	if len(commit.Precommits) == 0 {
 		return errors.New("No precommits in commit")
 	}
@@ -316,8 +314,10 @@ func (commit *Commit) StringIndented(indent string) string {
 		precommitStrings[i] = precommit.String()
 	}
 	return fmt.Sprintf(`Commit{
+%s  BlockID:    %v
 %s  Precommits: %v
 %s}#%X`,
+		indent, commit.BlockID,
 		indent, strings.Join(precommitStrings, "\n"+indent+"  "),
 		indent, commit.hash)
 }
@@ -360,3 +360,37 @@ func (data *Data) StringIndented(indent string) string {
 		indent, strings.Join(txStrings, "\n"+indent+"  "),
 		indent, data.hash)
 }
+
+//--------------------------------------------------------------------------------
+
+type BlockID struct {
+	Hash        []byte        `json:"hash"`
+	PartsHeader PartSetHeader `json:"parts"`
+}
+
+func (blockID BlockID) IsZero() bool {
+	return len(blockID.Hash) == 0 && blockID.PartsHeader.IsZero()
+}
+
+func (blockID BlockID) Equals(other BlockID) bool {
+	return bytes.Equal(blockID.Hash, other.Hash) &&
+		blockID.PartsHeader.Equals(other.PartsHeader)
+}
+
+func (blockID BlockID) Key() string {
+	return string(blockID.Hash) + string(wire.BinaryBytes(blockID.PartsHeader))
+}
+
+func (blockID BlockID) WriteSignBytes(w io.Writer, n *int, err *error) {
+	if blockID.IsZero() {
+		wire.WriteTo([]byte("null"), w, n, err)
+	} else {
+		wire.WriteTo([]byte(Fmt(`{"hash":"%X","parts":`, blockID.Hash)), w, n, err)
+		blockID.PartsHeader.WriteSignBytes(w, n, err)
+		wire.WriteTo([]byte("}"), w, n, err)
+	}
+}
+
+func (blockID BlockID) String() string {
+	return fmt.Sprintf(`%X:%v`, blockID.Hash, blockID.PartsHeader)
+}
diff --git a/types/events.go b/types/events.go
index 4fe4d407..fc7e0ac6 100644
--- a/types/events.go
+++ b/types/events.go
@@ -91,9 +91,7 @@ type EventDataRoundState struct {
 }
 
 type EventDataVote struct {
-	Index   int
-	Address []byte
-	Vote    *Vote
+	Vote *Vote
 }
 
 func (_ EventDataNewBlock) AssertIsTMEventData()       {}
diff --git a/types/part_set.go b/types/part_set.go
index bdf198d9..f132c5fe 100644
--- a/types/part_set.go
+++ b/types/part_set.go
@@ -14,10 +14,6 @@ import (
 	"github.com/tendermint/go-wire"
 )
 
-const (
-	partSize = 65536 // 64KB ...  4096 // 4KB
-)
-
 var (
 	ErrPartSetUnexpectedIndex = errors.New("Error part set unexpected index")
 	ErrPartSetInvalidProof    = errors.New("Error part set invalid proof")
@@ -66,7 +62,7 @@ type PartSetHeader struct {
 }
 
 func (psh PartSetHeader) String() string {
-	return fmt.Sprintf("PartSet{T:%v %X}", psh.Total, Fingerprint(psh.Hash))
+	return fmt.Sprintf("%v:%X", psh.Total, Fingerprint(psh.Hash))
 }
 
 func (psh PartSetHeader) IsZero() bool {
@@ -95,7 +91,7 @@ type PartSet struct {
 
 // Returns an immutable, full PartSet from the data bytes.
 // The data bytes are split into "partSize" chunks, and merkle tree computed.
-func NewPartSetFromData(data []byte) *PartSet {
+func NewPartSetFromData(data []byte, partSize int) *PartSet {
 	// divide data into 4kb parts.
 	total := (len(data) + partSize - 1) / partSize
 	parts := make([]*Part, total)
diff --git a/types/part_set_test.go b/types/part_set_test.go
index bbc3da9e..6e25752d 100644
--- a/types/part_set_test.go
+++ b/types/part_set_test.go
@@ -8,12 +8,16 @@ import (
 	. "github.com/tendermint/go-common"
 )
 
+const (
+	testPartSize = 65536 // 64KB ...  4096 // 4KB
+)
+
 func TestBasicPartSet(t *testing.T) {
 
 	// Construct random data of size partSize * 100
-	data := RandBytes(partSize * 100)
+	data := RandBytes(testPartSize * 100)
 
-	partSet := NewPartSetFromData(data)
+	partSet := NewPartSetFromData(data, testPartSize)
 	if len(partSet.Hash()) == 0 {
 		t.Error("Expected to get hash")
 	}
@@ -61,8 +65,8 @@ func TestBasicPartSet(t *testing.T) {
 func TestWrongProof(t *testing.T) {
 
 	// Construct random data of size partSize * 100
-	data := RandBytes(partSize * 100)
-	partSet := NewPartSetFromData(data)
+	data := RandBytes(testPartSize * 100)
+	partSet := NewPartSetFromData(data, testPartSize)
 
 	// Test adding a part with wrong data.
 	partSet2 := NewPartSetFromHeader(partSet.Header())
diff --git a/types/priv_validator.go b/types/priv_validator.go
index 5700fdf5..e54bc4d5 100644
--- a/types/priv_validator.go
+++ b/types/priv_validator.go
@@ -163,6 +163,10 @@ func (privVal *PrivValidator) Reset() {
 	privVal.Save()
 }
 
+func (privVal *PrivValidator) GetAddress() []byte {
+	return privVal.Address
+}
+
 func (privVal *PrivValidator) SignVote(chainID string, vote *Vote) error {
 	privVal.mtx.Lock()
 	defer privVal.mtx.Unlock()
@@ -231,6 +235,7 @@ func (privVal *PrivValidator) signBytesHRS(height, round int, step int8, signByt
 	privVal.save()
 
 	return signature, nil
+
 }
 
 func (privVal *PrivValidator) String() string {
diff --git a/types/proposal.go b/types/proposal.go
index d69b6064..85ac5f06 100644
--- a/types/proposal.go
+++ b/types/proposal.go
@@ -19,29 +19,33 @@ type Proposal struct {
 	Height           int                     `json:"height"`
 	Round            int                     `json:"round"`
 	BlockPartsHeader PartSetHeader           `json:"block_parts_header"`
-	POLRound         int                     `json:"pol_round"` // -1 if null.
+	POLRound         int                     `json:"pol_round"`    // -1 if null.
+	POLBlockID       BlockID                 `json:"pol_block_id"` // zero if null.
 	Signature        crypto.SignatureEd25519 `json:"signature"`
 }
 
 // polRound: -1 if no polRound.
-func NewProposal(height int, round int, blockPartsHeader PartSetHeader, polRound int) *Proposal {
+func NewProposal(height int, round int, blockPartsHeader PartSetHeader, polRound int, polBlockID BlockID) *Proposal {
 	return &Proposal{
 		Height:           height,
 		Round:            round,
 		BlockPartsHeader: blockPartsHeader,
 		POLRound:         polRound,
+		POLBlockID:       polBlockID,
 	}
 }
 
 func (p *Proposal) String() string {
-	return fmt.Sprintf("Proposal{%v/%v %v %v %v}", p.Height, p.Round,
-		p.BlockPartsHeader, p.POLRound, p.Signature)
+	return fmt.Sprintf("Proposal{%v/%v %v (%v,%v) %v}", p.Height, p.Round,
+		p.BlockPartsHeader, p.POLRound, p.POLBlockID, p.Signature)
 }
 
 func (p *Proposal) WriteSignBytes(chainID string, w io.Writer, n *int, err *error) {
 	wire.WriteTo([]byte(Fmt(`{"chain_id":"%s"`, chainID)), w, n, err)
 	wire.WriteTo([]byte(`,"proposal":{"block_parts_header":`), w, n, err)
 	p.BlockPartsHeader.WriteSignBytes(w, n, err)
-	wire.WriteTo([]byte(Fmt(`,"height":%v,"pol_round":%v`, p.Height, p.POLRound)), w, n, err)
+	wire.WriteTo([]byte(Fmt(`,"height":%v,"pol_block_id":`, p.Height)), w, n, err)
+	p.POLBlockID.WriteSignBytes(w, n, err)
+	wire.WriteTo([]byte(Fmt(`,"pol_round":%v`, p.POLRound)), w, n, err)
 	wire.WriteTo([]byte(Fmt(`,"round":%v}}`, p.Round)), w, n, err)
 }
diff --git a/types/proposal_test.go b/types/proposal_test.go
index ea3dac2b..1d8c6205 100644
--- a/types/proposal_test.go
+++ b/types/proposal_test.go
@@ -14,8 +14,8 @@ func TestProposalSignable(t *testing.T) {
 	signBytes := SignBytes("test_chain_id", proposal)
 	signStr := string(signBytes)
 
-	expected := `{"chain_id":"test_chain_id","proposal":{"block_parts_header":{"hash":"626C6F636B7061727473","total":111},"height":12345,"pol_round":-1,"round":23456}}`
+	expected := `{"chain_id":"test_chain_id","proposal":{"block_parts_header":{"hash":"626C6F636B7061727473","total":111},"height":12345,"pol_block_id":null,"pol_round":-1,"round":23456}}`
 	if signStr != expected {
-		t.Errorf("Got unexpected sign string for SendTx. Expected:\n%v\nGot:\n%v", expected, signStr)
+		t.Errorf("Got unexpected sign string for Proposal. Expected:\n%v\nGot:\n%v", expected, signStr)
 	}
 }
diff --git a/types/validator_set.go b/types/validator_set.go
index 5a51c79f..92400f67 100644
--- a/types/validator_set.go
+++ b/types/validator_set.go
@@ -206,8 +206,7 @@ func (valSet *ValidatorSet) Iterate(fn func(index int, val *Validator) bool) {
 }
 
 // Verify that +2/3 of the set had signed the given signBytes
-func (valSet *ValidatorSet) VerifyCommit(chainID string,
-	hash []byte, parts PartSetHeader, height int, commit *Commit) error {
+func (valSet *ValidatorSet) VerifyCommit(chainID string, blockID BlockID, height int, commit *Commit) error {
 	if valSet.Size() != len(commit.Precommits) {
 		return fmt.Errorf("Invalid commit -- wrong set size: %v vs %v", valSet.Size(), len(commit.Precommits))
 	}
@@ -238,10 +237,7 @@ func (valSet *ValidatorSet) VerifyCommit(chainID string,
 		if !val.PubKey.VerifyBytes(precommitSignBytes, precommit.Signature) {
 			return fmt.Errorf("Invalid commit -- invalid signature: %v", precommit)
 		}
-		if !bytes.Equal(precommit.BlockHash, hash) {
-			continue // Not an error, but doesn't count
-		}
-		if !parts.Equals(precommit.BlockPartsHeader) {
+		if !blockID.Equals(precommit.BlockID) {
 			continue // Not an error, but doesn't count
 		}
 		// Good precommit!
@@ -313,6 +309,7 @@ func (ac accumComparable) Less(o interface{}) bool {
 //----------------------------------------
 // For testing
 
+// NOTE: PrivValidator are in order.
 func RandValidatorSet(numValidators int, votingPower int64) (*ValidatorSet, []*PrivValidator) {
 	vals := make([]*Validator, numValidators)
 	privValidators := make([]*PrivValidator, numValidators)
diff --git a/types/vote.go b/types/vote.go
index 67936927..92d99f48 100644
--- a/types/vote.go
+++ b/types/vote.go
@@ -11,40 +11,55 @@ import (
 )
 
 var (
-	ErrVoteUnexpectedStep   = errors.New("Unexpected step")
-	ErrVoteInvalidAccount   = errors.New("Invalid round vote account")
-	ErrVoteInvalidSignature = errors.New("Invalid round vote signature")
-	ErrVoteInvalidBlockHash = errors.New("Invalid block hash")
+	ErrVoteUnexpectedStep          = errors.New("Unexpected step")
+	ErrVoteInvalidValidatorIndex   = errors.New("Invalid round vote validator index")
+	ErrVoteInvalidValidatorAddress = errors.New("Invalid round vote validator address")
+	ErrVoteInvalidSignature        = errors.New("Invalid round vote signature")
+	ErrVoteInvalidBlockHash        = errors.New("Invalid block hash")
 )
 
-type ErrVoteConflictingSignature struct {
+type ErrVoteConflictingVotes struct {
 	VoteA *Vote
 	VoteB *Vote
 }
 
-func (err *ErrVoteConflictingSignature) Error() string {
-	return "Conflicting round vote signature"
-}
-
-// Represents a prevote, precommit, or commit vote from validators for consensus.
-type Vote struct {
-	Height           int                     `json:"height"`
-	Round            int                     `json:"round"`
-	Type             byte                    `json:"type"`
-	BlockHash        []byte                  `json:"block_hash"`         // empty if vote is nil.
-	BlockPartsHeader PartSetHeader           `json:"block_parts_header"` // zero if vote is nil.
-	Signature        crypto.SignatureEd25519 `json:"signature"`
+func (err *ErrVoteConflictingVotes) Error() string {
+	return "Conflicting votes"
 }
 
 // Types of votes
+// TODO Make a new type "VoteType"
 const (
 	VoteTypePrevote   = byte(0x01)
 	VoteTypePrecommit = byte(0x02)
 )
 
+func IsVoteTypeValid(type_ byte) bool {
+	switch type_ {
+	case VoteTypePrevote:
+		return true
+	case VoteTypePrecommit:
+		return true
+	default:
+		return false
+	}
+}
+
+// Represents a prevote, precommit, or commit vote from validators for consensus.
+type Vote struct {
+	ValidatorAddress []byte                  `json:"validator_address"`
+	ValidatorIndex   int                     `json:"validator_index"`
+	Height           int                     `json:"height"`
+	Round            int                     `json:"round"`
+	Type             byte                    `json:"type"`
+	BlockID          BlockID                 `json:"block_id"` // zero if vote is nil.
+	Signature        crypto.SignatureEd25519 `json:"signature"`
+}
+
 func (vote *Vote) WriteSignBytes(chainID string, w io.Writer, n *int, err *error) {
 	wire.WriteTo([]byte(Fmt(`{"chain_id":"%s"`, chainID)), w, n, err)
-	wire.WriteTo([]byte(Fmt(`,"vote":{"block_hash":"%X","block_parts_header":%v`, vote.BlockHash, vote.BlockPartsHeader)), w, n, err)
+	wire.WriteTo([]byte(`,"vote":{"block_id":`), w, n, err)
+	vote.BlockID.WriteSignBytes(w, n, err)
 	wire.WriteTo([]byte(Fmt(`,"height":%v,"round":%v,"type":%v}}`, vote.Height, vote.Round, vote.Type)), w, n, err)
 }
 
@@ -67,5 +82,8 @@ func (vote *Vote) String() string {
 		PanicSanity("Unknown vote type")
 	}
 
-	return fmt.Sprintf("Vote{%v/%02d/%v(%v) %X#%v %v}", vote.Height, vote.Round, vote.Type, typeString, Fingerprint(vote.BlockHash), vote.BlockPartsHeader, vote.Signature)
+	return fmt.Sprintf("Vote{%v:%X %v/%02d/%v(%v) %X %v}",
+		vote.ValidatorIndex, Fingerprint(vote.ValidatorAddress),
+		vote.Height, vote.Round, vote.Type, typeString,
+		Fingerprint(vote.BlockID.Hash), vote.Signature)
 }
diff --git a/types/vote_set.go b/types/vote_set.go
index e701d461..e7598532 100644
--- a/types/vote_set.go
+++ b/types/vote_set.go
@@ -7,29 +7,56 @@ import (
 	"sync"
 
 	. "github.com/tendermint/go-common"
-	"github.com/tendermint/go-wire"
 )
 
-// VoteSet helps collect signatures from validators at each height+round
-// for a predefined vote type.
-// Note that there three kinds of votes: prevotes, precommits, and commits.
-// A commit of prior rounds can be added added in lieu of votes/precommits.
-// NOTE: Assumes that the sum total of voting power does not exceed MaxUInt64.
+/*
+	VoteSet helps collect signatures from validators at each height+round for a
+	predefined vote type.
+
+	We need VoteSet to be able to keep track of conflicting votes when validators
+	double-sign.  Yet, we can't keep track of *all* the votes seen, as that could
+	be a DoS attack vector.
+
+	There are two storage areas for votes.
+	1. voteSet.votes
+	2. voteSet.votesByBlock
+
+	`.votes` is the "canonical" list of votes.  It always has at least one vote,
+	if a vote from a validator had been seen at all.  Usually it keeps track of
+	the first vote seen, but when a 2/3 majority is found, votes for that get
+	priority and are copied over from `.votesByBlock`.
+
+	`.votesByBlock` keeps track of a list of votes for a particular block.  There
+	are two ways a &blockVotes{} gets created in `.votesByBlock`.
+	1. the first vote seen by a validator was for the particular block.
+	2. a peer claims to have seen 2/3 majority for the particular block.
+
+	Since the first vote from a validator will always get added in `.votesByBlock`
+	, all votes in `.votes` will have a corresponding entry in `.votesByBlock`.
+
+	When a &blockVotes{} in `.votesByBlock` reaches a 2/3 majority quorum, its
+	votes are copied into `.votes`.
+
+	All this is memory bounded because conflicting votes only get added if a peer
+	told us to track that block, each peer only gets to tell us 1 such block, and,
+	there's only a limited number of peers.
+
+	NOTE: Assumes that the sum total of voting power does not exceed MaxUInt64.
+*/
 type VoteSet struct {
 	chainID string
 	height  int
 	round   int
 	type_   byte
 
-	mtx              sync.Mutex
-	valSet           *ValidatorSet
-	votes            []*Vote          // validator index -> vote
-	votesBitArray    *BitArray        // validator index -> has vote?
-	votesByBlock     map[string]int64 // string(blockHash)+string(blockParts) -> vote sum.
-	totalVotes       int64
-	maj23Hash        []byte
-	maj23PartsHeader PartSetHeader
-	maj23Exists      bool
+	mtx           sync.Mutex
+	valSet        *ValidatorSet
+	votesBitArray *BitArray
+	votes         []*Vote                // Primary votes to share
+	sum           int64                  // Sum of voting power for seen votes, discounting conflicts
+	maj23         *BlockID               // First 2/3 majority seen
+	votesByBlock  map[string]*blockVotes // string(blockHash|blockParts) -> blockVotes
+	peerMaj23s    map[string]BlockID     // Maj23 for each peer
 }
 
 // Constructs a new VoteSet struct used to accumulate votes for given height/round.
@@ -43,10 +70,12 @@ func NewVoteSet(chainID string, height int, round int, type_ byte, valSet *Valid
 		round:         round,
 		type_:         type_,
 		valSet:        valSet,
-		votes:         make([]*Vote, valSet.Size()),
 		votesBitArray: NewBitArray(valSet.Size()),
-		votesByBlock:  make(map[string]int64),
-		totalVotes:    0,
+		votes:         make([]*Vote, valSet.Size()),
+		sum:           0,
+		maj23:         nil,
+		votesByBlock:  make(map[string]*blockVotes, valSet.Size()),
+		peerMaj23s:    make(map[string]BlockID),
 	}
 }
 
@@ -86,94 +115,197 @@ func (voteSet *VoteSet) Size() int {
 	}
 }
 
-// Returns added=true, index if vote was added
-// Otherwise returns err=ErrVote[UnexpectedStep|InvalidAccount|InvalidSignature|InvalidBlockHash|ConflictingSignature]
+// Returns added=true if vote is valid and new.
+// Otherwise returns err=ErrVote[
+//		UnexpectedStep | InvalidIndex | InvalidAddress |
+//		InvalidSignature | InvalidBlockHash | ConflictingVotes ]
 // Duplicate votes return added=false, err=nil.
+// Conflicting votes return added=*, err=ErrVoteConflictingVotes.
 // NOTE: vote should not be mutated after adding.
-func (voteSet *VoteSet) AddByIndex(valIndex int, vote *Vote) (added bool, address []byte, err error) {
+func (voteSet *VoteSet) AddVote(vote *Vote) (added bool, err error) {
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
 
-	return voteSet.addByIndex(valIndex, vote)
+	return voteSet.addVote(vote)
 }
 
-// Returns added=true, index if vote was added
-// Otherwise returns err=ErrVote[UnexpectedStep|InvalidAccount|InvalidSignature|InvalidBlockHash|ConflictingSignature]
-// Duplicate votes return added=false, err=nil.
-// NOTE: vote should not be mutated after adding.
-func (voteSet *VoteSet) AddByAddress(address []byte, vote *Vote) (added bool, index int, err error) {
-	voteSet.mtx.Lock()
-	defer voteSet.mtx.Unlock()
+// NOTE: Validates as much as possible before attempting to verify the signature.
+func (voteSet *VoteSet) addVote(vote *Vote) (added bool, err error) {
+	valIndex := vote.ValidatorIndex
+	valAddr := vote.ValidatorAddress
+	blockKey := vote.BlockID.Key()
 
-	// Ensure that signer is a validator.
-	valIndex, val := voteSet.valSet.GetByAddress(address)
-	if val == nil {
-		return false, 0, ErrVoteInvalidAccount
+	// Ensure that validator index was set
+	if valIndex < 0 || len(valAddr) == 0 {
+		panic("Validator index or address was not set in vote.")
 	}
 
-	return voteSet.addVote(val, valIndex, vote)
-}
-
-func (voteSet *VoteSet) addByIndex(valIndex int, vote *Vote) (added bool, address []byte, err error) {
-	// Ensure that signer is a validator.
-	address, val := voteSet.valSet.GetByIndex(valIndex)
-	if val == nil {
-		return false, nil, ErrVoteInvalidAccount
-	}
-
-	added, _, err = voteSet.addVote(val, valIndex, vote)
-	return
-}
-
-func (voteSet *VoteSet) addVote(val *Validator, valIndex int, vote *Vote) (bool, int, error) {
-
-	// Make sure the step matches. (or that vote is commit && round < voteSet.round)
+	// Make sure the step matches.
 	if (vote.Height != voteSet.height) ||
 		(vote.Round != voteSet.round) ||
 		(vote.Type != voteSet.type_) {
-		return false, 0, ErrVoteUnexpectedStep
+		return false, ErrVoteUnexpectedStep
 	}
 
-	// If vote already exists, return false.
-	if existingVote := voteSet.votes[valIndex]; existingVote != nil {
-		if bytes.Equal(existingVote.BlockHash, vote.BlockHash) {
-			return false, valIndex, nil
+	// Ensure that signer is a validator.
+	lookupAddr, val := voteSet.valSet.GetByIndex(valIndex)
+	if val == nil {
+		return false, ErrVoteInvalidValidatorIndex
+	}
+
+	// Ensure that the signer has the right address
+	if !bytes.Equal(valAddr, lookupAddr) {
+		return false, ErrVoteInvalidValidatorAddress
+	}
+
+	// If we already know of this vote, return false.
+	if existing, ok := voteSet.getVote(valIndex, blockKey); ok {
+		if existing.Signature.Equals(vote.Signature) {
+			return false, nil // duplicate
 		} else {
-			// Check signature.
-			if !val.PubKey.VerifyBytes(SignBytes(voteSet.chainID, vote), vote.Signature) {
-				// Bad signature.
-				return false, 0, ErrVoteInvalidSignature
-			}
-			return false, valIndex, &ErrVoteConflictingSignature{
-				VoteA: existingVote,
-				VoteB: vote,
-			}
+			return false, ErrVoteInvalidSignature // NOTE: assumes deterministic signatures
 		}
 	}
 
 	// Check signature.
 	if !val.PubKey.VerifyBytes(SignBytes(voteSet.chainID, vote), vote.Signature) {
 		// Bad signature.
-		return false, 0, ErrVoteInvalidSignature
+		return false, ErrVoteInvalidSignature
 	}
 
-	// Add vote.
-	voteSet.votes[valIndex] = vote
-	voteSet.votesBitArray.SetIndex(valIndex, true)
-	blockKey := string(vote.BlockHash) + string(wire.BinaryBytes(vote.BlockPartsHeader))
-	totalBlockHashVotes := voteSet.votesByBlock[blockKey] + val.VotingPower
-	voteSet.votesByBlock[blockKey] = totalBlockHashVotes
-	voteSet.totalVotes += val.VotingPower
-
-	// If we just nudged it up to two thirds majority, add it.
-	if totalBlockHashVotes > voteSet.valSet.TotalVotingPower()*2/3 &&
-		(totalBlockHashVotes-val.VotingPower) <= voteSet.valSet.TotalVotingPower()*2/3 {
-		voteSet.maj23Hash = vote.BlockHash
-		voteSet.maj23PartsHeader = vote.BlockPartsHeader
-		voteSet.maj23Exists = true
+	// Add vote and get conflicting vote if any
+	added, conflicting := voteSet.addVerifiedVote(vote, blockKey, val.VotingPower)
+	if conflicting != nil {
+		return added, &ErrVoteConflictingVotes{
+			VoteA: conflicting,
+			VoteB: vote,
+		}
+	} else {
+		if !added {
+			PanicSanity("Expected to add non-conflicting vote")
+		}
+		return added, nil
 	}
 
-	return true, valIndex, nil
+}
+
+// Returns (vote, true) if vote exists for valIndex and blockKey
+func (voteSet *VoteSet) getVote(valIndex int, blockKey string) (vote *Vote, ok bool) {
+	if existing := voteSet.votes[valIndex]; existing != nil && existing.BlockID.Key() == blockKey {
+		return existing, true
+	}
+	if existing := voteSet.votesByBlock[blockKey].getByIndex(valIndex); existing != nil {
+		return existing, true
+	}
+	return nil, false
+}
+
+// Assumes signature is valid.
+// If conflicting vote exists, returns it.
+func (voteSet *VoteSet) addVerifiedVote(vote *Vote, blockKey string, votingPower int64) (added bool, conflicting *Vote) {
+	valIndex := vote.ValidatorIndex
+
+	// Already exists in voteSet.votes?
+	if existing := voteSet.votes[valIndex]; existing != nil {
+		if existing.BlockID.Equals(vote.BlockID) {
+			PanicSanity("addVerifiedVote does not expect duplicate votes")
+		} else {
+			conflicting = existing
+		}
+		// Replace vote if blockKey matches voteSet.maj23.
+		if voteSet.maj23 != nil && voteSet.maj23.Key() == blockKey {
+			voteSet.votes[valIndex] = vote
+			voteSet.votesBitArray.SetIndex(valIndex, true)
+		}
+		// Otherwise don't add it to voteSet.votes
+	} else {
+		// Add to voteSet.votes and incr .sum
+		voteSet.votes[valIndex] = vote
+		voteSet.votesBitArray.SetIndex(valIndex, true)
+		voteSet.sum += votingPower
+	}
+
+	votesByBlock, ok := voteSet.votesByBlock[blockKey]
+	if ok {
+		if conflicting != nil && !votesByBlock.peerMaj23 {
+			// There's a conflict and no peer claims that this block is special.
+			return false, conflicting
+		}
+		// We'll add the vote in a bit.
+	} else {
+		// .votesByBlock doesn't exist...
+		if conflicting != nil {
+			// ... and there's a conflicting vote.
+			// We're not even tracking this blockKey, so just forget it.
+			return false, conflicting
+		} else {
+			// ... and there's no conflicting vote.
+			// Start tracking this blockKey
+			votesByBlock = newBlockVotes(false, voteSet.valSet.Size())
+			voteSet.votesByBlock[blockKey] = votesByBlock
+			// We'll add the vote in a bit.
+		}
+	}
+
+	// Before adding to votesByBlock, see if we'll exceed quorum
+	origSum := votesByBlock.sum
+	quorum := voteSet.valSet.TotalVotingPower()*2/3 + 1
+
+	// Add vote to votesByBlock
+	votesByBlock.addVerifiedVote(vote, votingPower)
+
+	// If we just crossed the quorum threshold and have 2/3 majority...
+	if origSum < quorum && quorum <= votesByBlock.sum {
+		// Only consider the first quorum reached
+		if voteSet.maj23 == nil {
+			maj23BlockID := vote.BlockID
+			voteSet.maj23 = &maj23BlockID
+			// And also copy votes over to voteSet.votes
+			for i, vote := range votesByBlock.votes {
+				if vote != nil {
+					voteSet.votes[i] = vote
+				}
+			}
+		}
+	}
+
+	return true, conflicting
+}
+
+// If a peer claims that it has 2/3 majority for given blockKey, call this.
+// NOTE: if there are too many peers, or too much peer churn,
+// this can cause memory issues.
+// TODO: implement ability to remove peers too
+func (voteSet *VoteSet) SetPeerMaj23(peerID string, blockID BlockID) {
+	voteSet.mtx.Lock()
+	defer voteSet.mtx.Unlock()
+
+	blockKey := blockID.Key()
+
+	// Make sure peer hasn't already told us something.
+	if existing, ok := voteSet.peerMaj23s[peerID]; ok {
+		if existing.Equals(blockID) {
+			return // Nothing to do
+		} else {
+			return // TODO bad peer!
+		}
+	}
+	voteSet.peerMaj23s[peerID] = blockID
+
+	// Create .votesByBlock entry if needed.
+	votesByBlock, ok := voteSet.votesByBlock[blockKey]
+	if ok {
+		if votesByBlock.peerMaj23 {
+			return // Nothing to do
+		} else {
+			votesByBlock.peerMaj23 = true
+			// No need to copy votes, already there.
+		}
+	} else {
+		votesByBlock = newBlockVotes(true, voteSet.valSet.Size())
+		voteSet.votesByBlock[blockKey] = votesByBlock
+		// No need to copy votes, no votes to copy over.
+	}
 }
 
 func (voteSet *VoteSet) BitArray() *BitArray {
@@ -185,6 +317,20 @@ func (voteSet *VoteSet) BitArray() *BitArray {
 	return voteSet.votesBitArray.Copy()
 }
 
+func (voteSet *VoteSet) BitArrayByBlockID(blockID BlockID) *BitArray {
+	if voteSet == nil {
+		return nil
+	}
+	voteSet.mtx.Lock()
+	defer voteSet.mtx.Unlock()
+	votesByBlock, ok := voteSet.votesByBlock[blockID.Key()]
+	if ok {
+		return votesByBlock.bitArray
+	}
+	return nil
+}
+
+// NOTE: if validator has conflicting votes, returns "canonical" vote
 func (voteSet *VoteSet) GetByIndex(valIndex int) *Vote {
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
@@ -207,7 +353,7 @@ func (voteSet *VoteSet) HasTwoThirdsMajority() bool {
 	}
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
-	return voteSet.maj23Exists
+	return voteSet.maj23 != nil
 }
 
 func (voteSet *VoteSet) IsCommit() bool {
@@ -219,7 +365,7 @@ func (voteSet *VoteSet) IsCommit() bool {
 	}
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
-	return len(voteSet.maj23Hash) > 0
+	return voteSet.maj23 != nil
 }
 
 func (voteSet *VoteSet) HasTwoThirdsAny() bool {
@@ -228,18 +374,18 @@ func (voteSet *VoteSet) HasTwoThirdsAny() bool {
 	}
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
-	return voteSet.totalVotes > voteSet.valSet.TotalVotingPower()*2/3
+	return voteSet.sum > voteSet.valSet.TotalVotingPower()*2/3
 }
 
 // Returns either a blockhash (or nil) that received +2/3 majority.
-// If there exists no such majority, returns (nil, false).
-func (voteSet *VoteSet) TwoThirdsMajority() (hash []byte, parts PartSetHeader, ok bool) {
+// If there exists no such majority, returns (nil, PartSetHeader{}, false).
+func (voteSet *VoteSet) TwoThirdsMajority() (blockID BlockID, ok bool) {
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
-	if voteSet.maj23Exists {
-		return voteSet.maj23Hash, voteSet.maj23PartsHeader, true
+	if voteSet.maj23 != nil {
+		return *voteSet.maj23, true
 	} else {
-		return nil, PartSetHeader{}, false
+		return BlockID{}, false
 	}
 }
 
@@ -263,10 +409,12 @@ func (voteSet *VoteSet) StringIndented(indent string) string {
 %s  H:%v R:%v T:%v
 %s  %v
 %s  %v
+%s  %v
 %s}`,
 		indent, voteSet.height, voteSet.round, voteSet.type_,
 		indent, strings.Join(voteStrings, "\n"+indent+"  "),
 		indent, voteSet.votesBitArray,
+		indent, voteSet.peerMaj23s,
 		indent)
 }
 
@@ -276,8 +424,8 @@ func (voteSet *VoteSet) StringShort() string {
 	}
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
-	return fmt.Sprintf(`VoteSet{H:%v R:%v T:%v +2/3:%v %v}`,
-		voteSet.height, voteSet.round, voteSet.type_, voteSet.maj23Exists, voteSet.votesBitArray)
+	return fmt.Sprintf(`VoteSet{H:%v R:%v T:%v +2/3:%v %v %v}`,
+		voteSet.height, voteSet.round, voteSet.type_, voteSet.maj23, voteSet.votesBitArray, voteSet.peerMaj23s)
 }
 
 //--------------------------------------------------------------------------------
@@ -289,30 +437,63 @@ func (voteSet *VoteSet) MakeCommit() *Commit {
 	}
 	voteSet.mtx.Lock()
 	defer voteSet.mtx.Unlock()
-	if len(voteSet.maj23Hash) == 0 {
+
+	// Make sure we have a 2/3 majority
+	if voteSet.maj23 == nil {
 		PanicSanity("Cannot MakeCommit() unless a blockhash has +2/3")
 	}
-	precommits := make([]*Vote, voteSet.valSet.Size())
-	voteSet.valSet.Iterate(func(valIndex int, val *Validator) bool {
-		vote := voteSet.votes[valIndex]
-		if vote == nil {
-			return false
-		}
-		if !bytes.Equal(vote.BlockHash, voteSet.maj23Hash) {
-			return false
-		}
-		if !vote.BlockPartsHeader.Equals(voteSet.maj23PartsHeader) {
-			return false
-		}
-		precommits[valIndex] = vote
-		return false
-	})
+
+	// For every validator, get the precommit
+	votesCopy := make([]*Vote, len(voteSet.votes))
+	copy(votesCopy, voteSet.votes)
 	return &Commit{
-		Precommits: precommits,
+		BlockID:    *voteSet.maj23,
+		Precommits: votesCopy,
 	}
 }
 
-//----------------------------------------
+//--------------------------------------------------------------------------------
+
+/*
+	Votes for a particular block
+	There are two ways a *blockVotes gets created for a blockKey.
+	1. first (non-conflicting) vote of a validator w/ blockKey (peerMaj23=false)
+	2. A peer claims to have a 2/3 majority w/ blockKey (peerMaj23=true)
+*/
+type blockVotes struct {
+	peerMaj23 bool      // peer claims to have maj23
+	bitArray  *BitArray // valIndex -> hasVote?
+	votes     []*Vote   // valIndex -> *Vote
+	sum       int64     // vote sum
+}
+
+func newBlockVotes(peerMaj23 bool, numValidators int) *blockVotes {
+	return &blockVotes{
+		peerMaj23: peerMaj23,
+		bitArray:  NewBitArray(numValidators),
+		votes:     make([]*Vote, numValidators),
+		sum:       0,
+	}
+}
+
+func (vs *blockVotes) addVerifiedVote(vote *Vote, votingPower int64) {
+	valIndex := vote.ValidatorIndex
+	if existing := vs.votes[valIndex]; existing == nil {
+		vs.bitArray.SetIndex(valIndex, true)
+		vs.votes[valIndex] = vote
+		vs.sum += votingPower
+	}
+}
+
+func (vs *blockVotes) getByIndex(index int) *Vote {
+	if vs == nil {
+		return nil
+	}
+	return vs.votes[index]
+}
+
+//--------------------------------------------------------------------------------
+
 // Common interface between *consensus.VoteSet and types.Commit
 type VoteSetReader interface {
 	Height() int
diff --git a/types/vote_set_test.go b/types/vote_set_test.go
index ffc3a9ef..19523a82 100644
--- a/types/vote_set_test.go
+++ b/types/vote_set_test.go
@@ -10,12 +10,21 @@ import (
 	"testing"
 )
 
-// Move it out?
+// NOTE: privValidators are in order
+// TODO: Move it out?
 func randVoteSet(height int, round int, type_ byte, numValidators int, votingPower int64) (*VoteSet, *ValidatorSet, []*PrivValidator) {
 	valSet, privValidators := RandValidatorSet(numValidators, votingPower)
 	return NewVoteSet("test_chain_id", height, round, type_, valSet), valSet, privValidators
 }
 
+// Convenience: Return new vote with different validator address/index
+func withValidator(vote *Vote, addr []byte, idx int) *Vote {
+	vote = vote.Copy()
+	vote.ValidatorAddress = addr
+	vote.ValidatorIndex = idx
+	return vote
+}
+
 // Convenience: Return new vote with different height
 func withHeight(vote *Vote, height int) *Vote {
 	vote = vote.Copy()
@@ -40,20 +49,20 @@ func withType(vote *Vote, type_ byte) *Vote {
 // Convenience: Return new vote with different blockHash
 func withBlockHash(vote *Vote, blockHash []byte) *Vote {
 	vote = vote.Copy()
-	vote.BlockHash = blockHash
+	vote.BlockID.Hash = blockHash
 	return vote
 }
 
 // Convenience: Return new vote with different blockParts
 func withBlockPartsHeader(vote *Vote, blockPartsHeader PartSetHeader) *Vote {
 	vote = vote.Copy()
-	vote.BlockPartsHeader = blockPartsHeader
+	vote.BlockID.PartsHeader = blockPartsHeader
 	return vote
 }
 
 func signAddVote(privVal *PrivValidator, vote *Vote, voteSet *VoteSet) (bool, error) {
 	vote.Signature = privVal.Sign(SignBytes(voteSet.ChainID(), vote)).(crypto.SignatureEd25519)
-	added, _, err := voteSet.AddByAddress(privVal.Address, vote)
+	added, err := voteSet.AddVote(vote)
 	return added, err
 }
 
@@ -70,12 +79,19 @@ func TestAddVote(t *testing.T) {
 	if voteSet.BitArray().GetIndex(0) {
 		t.Errorf("Expected BitArray.GetIndex(0) to be false")
 	}
-	hash, header, ok := voteSet.TwoThirdsMajority()
-	if hash != nil || !header.IsZero() || ok {
+	blockID, ok := voteSet.TwoThirdsMajority()
+	if ok || !blockID.IsZero() {
 		t.Errorf("There should be no 2/3 majority")
 	}
 
-	vote := &Vote{Height: height, Round: round, Type: VoteTypePrevote, BlockHash: nil}
+	vote := &Vote{
+		ValidatorAddress: val0.Address,
+		ValidatorIndex:   0, // since privValidators are in order
+		Height:           height,
+		Round:            round,
+		Type:             VoteTypePrevote,
+		BlockID:          BlockID{nil, PartSetHeader{}},
+	}
 	signAddVote(val0, vote, voteSet)
 
 	if voteSet.GetByAddress(val0.Address) == nil {
@@ -84,8 +100,8 @@ func TestAddVote(t *testing.T) {
 	if !voteSet.BitArray().GetIndex(0) {
 		t.Errorf("Expected BitArray.GetIndex(0) to be true")
 	}
-	hash, header, ok = voteSet.TwoThirdsMajority()
-	if hash != nil || !header.IsZero() || ok {
+	blockID, ok = voteSet.TwoThirdsMajority()
+	if ok || !blockID.IsZero() {
 		t.Errorf("There should be no 2/3 majority")
 	}
 }
@@ -94,31 +110,40 @@ func Test2_3Majority(t *testing.T) {
 	height, round := 1, 0
 	voteSet, _, privValidators := randVoteSet(height, round, VoteTypePrevote, 10, 1)
 
-	vote := &Vote{Height: height, Round: round, Type: VoteTypePrevote, BlockHash: nil}
-
+	voteProto := &Vote{
+		ValidatorAddress: nil, // NOTE: must fill in
+		ValidatorIndex:   -1,  // NOTE: must fill in
+		Height:           height,
+		Round:            round,
+		Type:             VoteTypePrevote,
+		BlockID:          BlockID{nil, PartSetHeader{}},
+	}
 	// 6 out of 10 voted for nil.
 	for i := 0; i < 6; i++ {
+		vote := withValidator(voteProto, privValidators[i].Address, i)
 		signAddVote(privValidators[i], vote, voteSet)
 	}
-	hash, header, ok := voteSet.TwoThirdsMajority()
-	if hash != nil || !header.IsZero() || ok {
+	blockID, ok := voteSet.TwoThirdsMajority()
+	if ok || !blockID.IsZero() {
 		t.Errorf("There should be no 2/3 majority")
 	}
 
 	// 7th validator voted for some blockhash
 	{
+		vote := withValidator(voteProto, privValidators[6].Address, 6)
 		signAddVote(privValidators[6], withBlockHash(vote, RandBytes(32)), voteSet)
-		hash, header, ok = voteSet.TwoThirdsMajority()
-		if hash != nil || !header.IsZero() || ok {
+		blockID, ok = voteSet.TwoThirdsMajority()
+		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority")
 		}
 	}
 
 	// 8th validator voted for nil.
 	{
+		vote := withValidator(voteProto, privValidators[7].Address, 7)
 		signAddVote(privValidators[7], vote, voteSet)
-		hash, header, ok = voteSet.TwoThirdsMajority()
-		if hash != nil || !header.IsZero() || !ok {
+		blockID, ok = voteSet.TwoThirdsMajority()
+		if !ok || !blockID.IsZero() {
 			t.Errorf("There should be 2/3 majority for nil")
 		}
 	}
@@ -132,60 +157,73 @@ func Test2_3MajorityRedux(t *testing.T) {
 	blockPartsTotal := 123
 	blockPartsHeader := PartSetHeader{blockPartsTotal, crypto.CRandBytes(32)}
 
-	vote := &Vote{Height: height, Round: round, Type: VoteTypePrevote, BlockHash: blockHash, BlockPartsHeader: blockPartsHeader}
+	voteProto := &Vote{
+		ValidatorAddress: nil, // NOTE: must fill in
+		ValidatorIndex:   -1,  // NOTE: must fill in
+		Height:           height,
+		Round:            round,
+		Type:             VoteTypePrevote,
+		BlockID:          BlockID{blockHash, blockPartsHeader},
+	}
 
 	// 66 out of 100 voted for nil.
 	for i := 0; i < 66; i++ {
+		vote := withValidator(voteProto, privValidators[i].Address, i)
 		signAddVote(privValidators[i], vote, voteSet)
 	}
-	hash, header, ok := voteSet.TwoThirdsMajority()
-	if hash != nil || !header.IsZero() || ok {
+	blockID, ok := voteSet.TwoThirdsMajority()
+	if ok || !blockID.IsZero() {
 		t.Errorf("There should be no 2/3 majority")
 	}
 
 	// 67th validator voted for nil
 	{
+		vote := withValidator(voteProto, privValidators[66].Address, 66)
 		signAddVote(privValidators[66], withBlockHash(vote, nil), voteSet)
-		hash, header, ok = voteSet.TwoThirdsMajority()
-		if hash != nil || !header.IsZero() || ok {
+		blockID, ok = voteSet.TwoThirdsMajority()
+		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added was nil")
 		}
 	}
 
 	// 68th validator voted for a different BlockParts PartSetHeader
 	{
+		vote := withValidator(voteProto, privValidators[67].Address, 67)
 		blockPartsHeader := PartSetHeader{blockPartsTotal, crypto.CRandBytes(32)}
 		signAddVote(privValidators[67], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
-		hash, header, ok = voteSet.TwoThirdsMajority()
-		if hash != nil || !header.IsZero() || ok {
+		blockID, ok = voteSet.TwoThirdsMajority()
+		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added had different PartSetHeader Hash")
 		}
 	}
 
 	// 69th validator voted for different BlockParts Total
 	{
+		vote := withValidator(voteProto, privValidators[68].Address, 68)
 		blockPartsHeader := PartSetHeader{blockPartsTotal + 1, blockPartsHeader.Hash}
 		signAddVote(privValidators[68], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
-		hash, header, ok = voteSet.TwoThirdsMajority()
-		if hash != nil || !header.IsZero() || ok {
+		blockID, ok = voteSet.TwoThirdsMajority()
+		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added had different PartSetHeader Total")
 		}
 	}
 
 	// 70th validator voted for different BlockHash
 	{
+		vote := withValidator(voteProto, privValidators[69].Address, 69)
 		signAddVote(privValidators[69], withBlockHash(vote, RandBytes(32)), voteSet)
-		hash, header, ok = voteSet.TwoThirdsMajority()
-		if hash != nil || !header.IsZero() || ok {
+		blockID, ok = voteSet.TwoThirdsMajority()
+		if ok || !blockID.IsZero() {
 			t.Errorf("There should be no 2/3 majority: last vote added had different BlockHash")
 		}
 	}
 
 	// 71st validator voted for the right BlockHash & BlockPartsHeader
 	{
+		vote := withValidator(voteProto, privValidators[70].Address, 70)
 		signAddVote(privValidators[70], vote, voteSet)
-		hash, header, ok = voteSet.TwoThirdsMajority()
-		if !bytes.Equal(hash, blockHash) || !header.Equals(blockPartsHeader) || !ok {
+		blockID, ok = voteSet.TwoThirdsMajority()
+		if !ok || !blockID.Equals(BlockID{blockHash, blockPartsHeader}) {
 			t.Errorf("There should be 2/3 majority")
 		}
 	}
@@ -195,48 +233,207 @@ func TestBadVotes(t *testing.T) {
 	height, round := 1, 0
 	voteSet, _, privValidators := randVoteSet(height, round, VoteTypePrevote, 10, 1)
 
+	voteProto := &Vote{
+		ValidatorAddress: nil,
+		ValidatorIndex:   -1,
+		Height:           height,
+		Round:            round,
+		Type:             VoteTypePrevote,
+		BlockID:          BlockID{nil, PartSetHeader{}},
+	}
+
 	// val0 votes for nil.
-	vote := &Vote{Height: height, Round: round, Type: VoteTypePrevote, BlockHash: nil}
-	added, err := signAddVote(privValidators[0], vote, voteSet)
-	if !added || err != nil {
-		t.Errorf("Expected VoteSet.Add to succeed")
+	{
+		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		added, err := signAddVote(privValidators[0], vote, voteSet)
+		if !added || err != nil {
+			t.Errorf("Expected VoteSet.Add to succeed")
+		}
 	}
 
 	// val0 votes again for some block.
-	added, err = signAddVote(privValidators[0], withBlockHash(vote, RandBytes(32)), voteSet)
-	if added || err == nil {
-		t.Errorf("Expected VoteSet.Add to fail, dupeout.")
+	{
+		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		added, err := signAddVote(privValidators[0], withBlockHash(vote, RandBytes(32)), voteSet)
+		if added || err == nil {
+			t.Errorf("Expected VoteSet.Add to fail, conflicting vote.")
+		}
 	}
 
 	// val1 votes on another height
-	added, err = signAddVote(privValidators[1], withHeight(vote, height+1), voteSet)
-	if added {
-		t.Errorf("Expected VoteSet.Add to fail, wrong height")
+	{
+		vote := withValidator(voteProto, privValidators[1].Address, 1)
+		added, err := signAddVote(privValidators[1], withHeight(vote, height+1), voteSet)
+		if added || err == nil {
+			t.Errorf("Expected VoteSet.Add to fail, wrong height")
+		}
 	}
 
 	// val2 votes on another round
-	added, err = signAddVote(privValidators[2], withRound(vote, round+1), voteSet)
-	if added {
-		t.Errorf("Expected VoteSet.Add to fail, wrong round")
+	{
+		vote := withValidator(voteProto, privValidators[2].Address, 2)
+		added, err := signAddVote(privValidators[2], withRound(vote, round+1), voteSet)
+		if added || err == nil {
+			t.Errorf("Expected VoteSet.Add to fail, wrong round")
+		}
 	}
 
 	// val3 votes of another type.
-	added, err = signAddVote(privValidators[3], withType(vote, VoteTypePrecommit), voteSet)
-	if added {
-		t.Errorf("Expected VoteSet.Add to fail, wrong type")
+	{
+		vote := withValidator(voteProto, privValidators[3].Address, 3)
+		added, err := signAddVote(privValidators[3], withType(vote, VoteTypePrecommit), voteSet)
+		if added || err == nil {
+			t.Errorf("Expected VoteSet.Add to fail, wrong type")
+		}
 	}
 }
 
+func TestConflicts(t *testing.T) {
+	height, round := 1, 0
+	voteSet, _, privValidators := randVoteSet(height, round, VoteTypePrevote, 4, 1)
+	blockHash1 := RandBytes(32)
+	blockHash2 := RandBytes(32)
+
+	voteProto := &Vote{
+		ValidatorAddress: nil,
+		ValidatorIndex:   -1,
+		Height:           height,
+		Round:            round,
+		Type:             VoteTypePrevote,
+		BlockID:          BlockID{nil, PartSetHeader{}},
+	}
+
+	// val0 votes for nil.
+	{
+		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		added, err := signAddVote(privValidators[0], vote, voteSet)
+		if !added || err != nil {
+			t.Errorf("Expected VoteSet.Add to succeed")
+		}
+	}
+
+	// val0 votes again for blockHash1.
+	{
+		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		added, err := signAddVote(privValidators[0], withBlockHash(vote, blockHash1), voteSet)
+		if added {
+			t.Errorf("Expected VoteSet.Add to fail, conflicting vote.")
+		}
+		if err == nil {
+			t.Errorf("Expected VoteSet.Add to return error, conflicting vote.")
+		}
+	}
+
+	// start tracking blockHash1
+	voteSet.SetPeerMaj23("peerA", BlockID{blockHash1, PartSetHeader{}})
+
+	// val0 votes again for blockHash1.
+	{
+		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		added, err := signAddVote(privValidators[0], withBlockHash(vote, blockHash1), voteSet)
+		if !added {
+			t.Errorf("Expected VoteSet.Add to succeed, called SetPeerMaj23().")
+		}
+		if err == nil {
+			t.Errorf("Expected VoteSet.Add to return error, conflicting vote.")
+		}
+	}
+
+	// attempt tracking blockHash2, should fail because already set for peerA.
+	voteSet.SetPeerMaj23("peerA", BlockID{blockHash2, PartSetHeader{}})
+
+	// val0 votes again for blockHash1.
+	{
+		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		added, err := signAddVote(privValidators[0], withBlockHash(vote, blockHash2), voteSet)
+		if added {
+			t.Errorf("Expected VoteSet.Add to fail, duplicate SetPeerMaj23() from peerA")
+		}
+		if err == nil {
+			t.Errorf("Expected VoteSet.Add to return error, conflicting vote.")
+		}
+	}
+
+	// val1 votes for blockHash1.
+	{
+		vote := withValidator(voteProto, privValidators[1].Address, 1)
+		added, err := signAddVote(privValidators[1], withBlockHash(vote, blockHash1), voteSet)
+		if !added || err != nil {
+			t.Errorf("Expected VoteSet.Add to succeed")
+		}
+	}
+
+	// check
+	if voteSet.HasTwoThirdsMajority() {
+		t.Errorf("We shouldn't have 2/3 majority yet")
+	}
+	if voteSet.HasTwoThirdsAny() {
+		t.Errorf("We shouldn't have 2/3 if any votes yet")
+	}
+
+	// val2 votes for blockHash2.
+	{
+		vote := withValidator(voteProto, privValidators[2].Address, 2)
+		added, err := signAddVote(privValidators[2], withBlockHash(vote, blockHash2), voteSet)
+		if !added || err != nil {
+			t.Errorf("Expected VoteSet.Add to succeed")
+		}
+	}
+
+	// check
+	if voteSet.HasTwoThirdsMajority() {
+		t.Errorf("We shouldn't have 2/3 majority yet")
+	}
+	if !voteSet.HasTwoThirdsAny() {
+		t.Errorf("We should have 2/3 if any votes")
+	}
+
+	// now attempt tracking blockHash1
+	voteSet.SetPeerMaj23("peerB", BlockID{blockHash1, PartSetHeader{}})
+
+	// val2 votes for blockHash1.
+	{
+		vote := withValidator(voteProto, privValidators[2].Address, 2)
+		added, err := signAddVote(privValidators[2], withBlockHash(vote, blockHash1), voteSet)
+		if !added {
+			t.Errorf("Expected VoteSet.Add to succeed")
+		}
+		if err == nil {
+			t.Errorf("Expected VoteSet.Add to return error, conflicting vote")
+		}
+	}
+
+	// check
+	if !voteSet.HasTwoThirdsMajority() {
+		t.Errorf("We should have 2/3 majority for blockHash1")
+	}
+	blockIDMaj23, _ := voteSet.TwoThirdsMajority()
+	if !bytes.Equal(blockIDMaj23.Hash, blockHash1) {
+		t.Errorf("Got the wrong 2/3 majority blockhash")
+	}
+	if !voteSet.HasTwoThirdsAny() {
+		t.Errorf("We should have 2/3 if any votes")
+	}
+
+}
+
 func TestMakeCommit(t *testing.T) {
 	height, round := 1, 0
 	voteSet, _, privValidators := randVoteSet(height, round, VoteTypePrecommit, 10, 1)
 	blockHash, blockPartsHeader := crypto.CRandBytes(32), PartSetHeader{123, crypto.CRandBytes(32)}
 
-	vote := &Vote{Height: height, Round: round, Type: VoteTypePrecommit,
-		BlockHash: blockHash, BlockPartsHeader: blockPartsHeader}
+	voteProto := &Vote{
+		ValidatorAddress: nil,
+		ValidatorIndex:   -1,
+		Height:           height,
+		Round:            round,
+		Type:             VoteTypePrecommit,
+		BlockID:          BlockID{blockHash, blockPartsHeader},
+	}
 
 	// 6 out of 10 voted for some block.
 	for i := 0; i < 6; i++ {
+		vote := withValidator(voteProto, privValidators[i].Address, i)
 		signAddVote(privValidators[i], vote, voteSet)
 	}
 
@@ -245,13 +442,15 @@ func TestMakeCommit(t *testing.T) {
 
 	// 7th voted for some other block.
 	{
-		vote := withBlockHash(vote, RandBytes(32))
+		vote := withValidator(voteProto, privValidators[6].Address, 6)
+		vote = withBlockHash(vote, RandBytes(32))
 		vote = withBlockPartsHeader(vote, PartSetHeader{123, RandBytes(32)})
 		signAddVote(privValidators[6], vote, voteSet)
 	}
 
 	// The 8th voted like everyone else.
 	{
+		vote := withValidator(voteProto, privValidators[7].Address, 7)
 		signAddVote(privValidators[7], vote, voteSet)
 	}
 
diff --git a/types/vote_test.go b/types/vote_test.go
new file mode 100644
index 00000000..353acfaf
--- /dev/null
+++ b/types/vote_test.go
@@ -0,0 +1,30 @@
+package types
+
+import (
+	"testing"
+)
+
+func TestVoteSignable(t *testing.T) {
+	vote := &Vote{
+		ValidatorAddress: []byte("addr"),
+		ValidatorIndex:   56789,
+		Height:           12345,
+		Round:            23456,
+		Type:             byte(2),
+		BlockID: BlockID{
+			Hash: []byte("hash"),
+			PartsHeader: PartSetHeader{
+				Total: 1000000,
+				Hash:  []byte("parts_hash"),
+			},
+		},
+	}
+	signBytes := SignBytes("test_chain_id", vote)
+	signStr := string(signBytes)
+
+	expected := `{"chain_id":"test_chain_id","vote":{"block_id":{"hash":"68617368","parts":{"hash":"70617274735F68617368","total":1000000}},"height":12345,"round":23456,"type":2}}`
+	if signStr != expected {
+		// NOTE: when this fails, you probably want to fix up consensus/replay_test too
+		t.Errorf("Got unexpected sign string for Vote. Expected:\n%v\nGot:\n%v", expected, signStr)
+	}
+}