diff --git a/blockchain/pool.go b/blockchain/pool.go
index 099594c1..192165bf 100644
--- a/blockchain/pool.go
+++ b/blockchain/pool.go
@@ -60,32 +60,32 @@ func NewBlockPool(start uint, requestsCh chan<- BlockRequest, timeoutsCh chan<-
 	}
 }
 
-func (bp *BlockPool) Start() {
-	if atomic.CompareAndSwapInt32(&bp.running, 0, 1) {
+func (pool *BlockPool) Start() {
+	if atomic.CompareAndSwapInt32(&pool.running, 0, 1) {
 		log.Info("Starting BlockPool")
-		go bp.run()
+		go pool.run()
 	}
 }
 
-func (bp *BlockPool) Stop() {
-	if atomic.CompareAndSwapInt32(&bp.running, 1, 0) {
+func (pool *BlockPool) Stop() {
+	if atomic.CompareAndSwapInt32(&pool.running, 1, 0) {
 		log.Info("Stopping BlockPool")
-		bp.repeater.Stop()
+		pool.repeater.Stop()
 	}
 }
 
-func (bp *BlockPool) IsRunning() bool {
-	return atomic.LoadInt32(&bp.running) == 1
+func (pool *BlockPool) IsRunning() bool {
+	return atomic.LoadInt32(&pool.running) == 1
 }
 
 // Run spawns requests as needed.
-func (bp *BlockPool) run() {
+func (pool *BlockPool) run() {
 RUN_LOOP:
 	for {
-		if atomic.LoadInt32(&bp.running) == 0 {
+		if atomic.LoadInt32(&pool.running) == 0 {
 			break RUN_LOOP
 		}
-		height, numPending, numTotal := bp.GetStatus()
+		height, numPending, numTotal := pool.GetStatus()
 		log.Debug("BlockPool.run", "height", height, "numPending", numPending,
 			"numTotal", numTotal)
 		if numPending >= maxPendingRequests {
@@ -96,91 +96,91 @@ RUN_LOOP:
 			time.Sleep(requestIntervalMS * time.Millisecond)
 		} else {
 			// request for more blocks.
-			height := bp.nextHeight()
-			bp.makeRequest(height)
+			height := pool.nextHeight()
+			pool.makeRequest(height)
 		}
 	}
 }
 
-func (bp *BlockPool) GetStatus() (uint, int32, int32) {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) GetStatus() (uint, int32, int32) {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	return bp.height, bp.numPending, bp.numTotal
+	return pool.height, pool.numPending, pool.numTotal
 }
 
 // We need to see the second block's Validation to validate the first block.
 // So we peek two blocks at a time.
-func (bp *BlockPool) PeekTwoBlocks() (first *types.Block, second *types.Block) {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) PeekTwoBlocks() (first *types.Block, second *types.Block) {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	if r := bp.requests[bp.height]; r != nil {
+	if r := pool.requests[pool.height]; r != nil {
 		first = r.block
 	}
-	if r := bp.requests[bp.height+1]; r != nil {
+	if r := pool.requests[pool.height+1]; r != nil {
 		second = r.block
 	}
 	return
 }
 
-// Pop the first block at bp.height
+// Pop the first block at pool.height
 // It must have been validated by 'second'.Validation from PeekTwoBlocks().
-func (bp *BlockPool) PopRequest() {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) PopRequest() {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	if r := bp.requests[bp.height]; r == nil || r.block == nil {
+	if r := pool.requests[pool.height]; r == nil || r.block == nil {
 		panic("PopRequest() requires a valid block")
 	}
 
-	delete(bp.requests, bp.height)
-	bp.height++
-	bp.numTotal--
+	delete(pool.requests, pool.height)
+	pool.height++
+	pool.numTotal--
 }
 
-// Invalidates the block at bp.height.
+// Invalidates the block at pool.height.
 // Remove the peer and request from others.
-func (bp *BlockPool) RedoRequest(height uint) {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) RedoRequest(height uint) {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	request := bp.requests[height]
+	request := pool.requests[height]
 	if request.block == nil {
 		panic("Expected block to be non-nil")
 	}
-	bp.RemovePeer(request.peerId) // Lock on peersMtx.
+	pool.RemovePeer(request.peerId) // Lock on peersMtx.
 	request.block = nil
 	request.peerId = ""
-	bp.numPending++
+	pool.numPending++
 
-	go requestRoutine(bp, height)
+	go requestRoutine(pool, height)
 }
 
-func (bp *BlockPool) hasBlock(height uint) bool {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) hasBlock(height uint) bool {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	request := bp.requests[height]
+	request := pool.requests[height]
 	return request != nil && request.block != nil
 }
 
-func (bp *BlockPool) setPeerForRequest(height uint, peerId string) {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) setPeerForRequest(height uint, peerId string) {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	request := bp.requests[height]
+	request := pool.requests[height]
 	if request == nil {
 		return
 	}
 	request.peerId = peerId
 }
 
-func (bp *BlockPool) AddBlock(block *types.Block, peerId string) {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) AddBlock(block *types.Block, peerId string) {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	request := bp.requests[block.Height]
+	request := pool.requests[block.Height]
 	if request == nil {
 		return
 	}
@@ -191,23 +191,23 @@ func (bp *BlockPool) AddBlock(block *types.Block, peerId string) {
 		return
 	}
 	request.block = block
-	bp.numPending--
+	pool.numPending--
 }
 
-func (bp *BlockPool) getPeer(peerId string) *bpPeer {
-	bp.peersMtx.Lock() // Lock
-	defer bp.peersMtx.Unlock()
+func (pool *BlockPool) getPeer(peerId string) *bpPeer {
+	pool.peersMtx.Lock() // Lock
+	defer pool.peersMtx.Unlock()
 
-	peer := bp.peers[peerId]
+	peer := pool.peers[peerId]
 	return peer
 }
 
 // Sets the peer's blockchain height.
-func (bp *BlockPool) SetPeerHeight(peerId string, height uint) {
-	bp.peersMtx.Lock() // Lock
-	defer bp.peersMtx.Unlock()
+func (pool *BlockPool) SetPeerHeight(peerId string, height uint) {
+	pool.peersMtx.Lock() // Lock
+	defer pool.peersMtx.Unlock()
 
-	peer := bp.peers[peerId]
+	peer := pool.peers[peerId]
 	if peer != nil {
 		peer.height = height
 	} else {
@@ -216,24 +216,24 @@ func (bp *BlockPool) SetPeerHeight(peerId string, height uint) {
 			id:          peerId,
 			numRequests: 0,
 		}
-		bp.peers[peerId] = peer
+		pool.peers[peerId] = peer
 	}
 }
 
-func (bp *BlockPool) RemovePeer(peerId string) {
-	bp.peersMtx.Lock() // Lock
-	defer bp.peersMtx.Unlock()
+func (pool *BlockPool) RemovePeer(peerId string) {
+	pool.peersMtx.Lock() // Lock
+	defer pool.peersMtx.Unlock()
 
-	delete(bp.peers, peerId)
+	delete(pool.peers, peerId)
 }
 
 // Pick an available peer with at least the given minHeight.
 // If no peers are available, returns nil.
-func (bp *BlockPool) pickIncrAvailablePeer(minHeight uint) *bpPeer {
-	bp.peersMtx.Lock()
-	defer bp.peersMtx.Unlock()
+func (pool *BlockPool) pickIncrAvailablePeer(minHeight uint) *bpPeer {
+	pool.peersMtx.Lock()
+	defer pool.peersMtx.Unlock()
 
-	for _, peer := range bp.peers {
+	for _, peer := range pool.peers {
 		if peer.numRequests >= maxRequestsPerPeer {
 			continue
 		}
@@ -247,69 +247,69 @@ func (bp *BlockPool) pickIncrAvailablePeer(minHeight uint) *bpPeer {
 	return nil
 }
 
-func (bp *BlockPool) decrPeer(peerId string) {
-	bp.peersMtx.Lock()
-	defer bp.peersMtx.Unlock()
+func (pool *BlockPool) decrPeer(peerId string) {
+	pool.peersMtx.Lock()
+	defer pool.peersMtx.Unlock()
 
-	peer := bp.peers[peerId]
+	peer := pool.peers[peerId]
 	if peer == nil {
 		return
 	}
 	peer.numRequests--
 }
 
-func (bp *BlockPool) nextHeight() uint {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) nextHeight() uint {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
-	return bp.height + uint(bp.numTotal)
+	return pool.height + uint(pool.numTotal)
 }
 
-func (bp *BlockPool) makeRequest(height uint) {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) makeRequest(height uint) {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
 	request := &bpRequest{
 		height: height,
 		peerId: "",
 		block:  nil,
 	}
-	bp.requests[height] = request
+	pool.requests[height] = request
 
-	nextHeight := bp.height + uint(bp.numTotal)
+	nextHeight := pool.height + uint(pool.numTotal)
 	if nextHeight == height {
-		bp.numTotal++
-		bp.numPending++
+		pool.numTotal++
+		pool.numPending++
 	}
 
-	go requestRoutine(bp, height)
+	go requestRoutine(pool, height)
 }
 
-func (bp *BlockPool) sendRequest(height uint, peerId string) {
-	if atomic.LoadInt32(&bp.running) == 0 {
+func (pool *BlockPool) sendRequest(height uint, peerId string) {
+	if atomic.LoadInt32(&pool.running) == 0 {
 		return
 	}
-	bp.requestsCh <- BlockRequest{height, peerId}
+	pool.requestsCh <- BlockRequest{height, peerId}
 }
 
-func (bp *BlockPool) sendTimeout(peerId string) {
-	if atomic.LoadInt32(&bp.running) == 0 {
+func (pool *BlockPool) sendTimeout(peerId string) {
+	if atomic.LoadInt32(&pool.running) == 0 {
 		return
 	}
-	bp.timeoutsCh <- peerId
+	pool.timeoutsCh <- peerId
 }
 
-func (bp *BlockPool) debug() string {
-	bp.requestsMtx.Lock() // Lock
-	defer bp.requestsMtx.Unlock()
+func (pool *BlockPool) debug() string {
+	pool.requestsMtx.Lock() // Lock
+	defer pool.requestsMtx.Unlock()
 
 	str := ""
-	for h := bp.height; h < bp.height+uint(bp.numTotal); h++ {
-		if bp.requests[h] == nil {
+	for h := pool.height; h < pool.height+uint(pool.numTotal); h++ {
+		if pool.requests[h] == nil {
 			str += Fmt("H(%v):X ", h)
 		} else {
 			str += Fmt("H(%v):", h)
-			str += Fmt("B?(%v) ", bp.requests[h].block != nil)
+			str += Fmt("B?(%v) ", pool.requests[h].block != nil)
 		}
 	}
 	return str
@@ -333,15 +333,15 @@ type bpRequest struct {
 
 // Responsible for making more requests as necessary
 // Returns when a block is found (e.g. AddBlock() is called)
-func requestRoutine(bp *BlockPool, height uint) {
+func requestRoutine(pool *BlockPool, height uint) {
 	for {
 		var peer *bpPeer = nil
 	PICK_LOOP:
 		for {
-			if !bp.IsRunning() {
+			if !pool.IsRunning() {
 				return
 			}
-			peer = bp.pickIncrAvailablePeer(height)
+			peer = pool.pickIncrAvailablePeer(height)
 			if peer == nil {
 				time.Sleep(requestIntervalMS * time.Millisecond)
 				continue PICK_LOOP
@@ -349,24 +349,24 @@ func requestRoutine(bp *BlockPool, height uint) {
 			break PICK_LOOP
 		}
 
-		bp.setPeerForRequest(height, peer.id)
+		pool.setPeerForRequest(height, peer.id)
 
 		for try := 0; try < maxTries; try++ {
-			bp.sendRequest(height, peer.id)
+			pool.sendRequest(height, peer.id)
 			time.Sleep(requestTimeoutSeconds * time.Second)
-			if bp.hasBlock(height) {
-				bp.decrPeer(peer.id)
+			if pool.hasBlock(height) {
+				pool.decrPeer(peer.id)
 				return
 			}
-			bpHeight, _, _ := bp.GetStatus()
+			bpHeight, _, _ := pool.GetStatus()
 			if height < bpHeight {
-				bp.decrPeer(peer.id)
+				pool.decrPeer(peer.id)
 				return
 			}
 		}
 
-		bp.RemovePeer(peer.id)
-		bp.sendTimeout(peer.id)
+		pool.RemovePeer(peer.id)
+		pool.sendTimeout(peer.id)
 	}
 }
 
diff --git a/blockchain/reactor.go b/blockchain/reactor.go
index 1aba782e..e5976877 100644
--- a/blockchain/reactor.go
+++ b/blockchain/reactor.go
@@ -8,7 +8,9 @@ import (
 	"time"
 
 	"github.com/tendermint/tendermint/binary"
+	. "github.com/tendermint/tendermint/common"
 	"github.com/tendermint/tendermint/p2p"
+	sm "github.com/tendermint/tendermint/state"
 	"github.com/tendermint/tendermint/types"
 )
 
@@ -16,11 +18,17 @@ const (
 	BlockchainChannel      = byte(0x40)
 	defaultChannelCapacity = 100
 	defaultSleepIntervalMS = 500
+	trySyncIntervalMS      = 100
+
+	// stop syncing when last block's time is
+	// within this much of the system time.
+	stopSyncingDurationMinutes = 10
 )
 
 // BlockchainReactor handles long-term catchup syncing.
 type BlockchainReactor struct {
 	sw         *p2p.Switch
+	state      *sm.State
 	store      *BlockStore
 	pool       *BlockPool
 	requestsCh chan BlockRequest
@@ -31,7 +39,10 @@ type BlockchainReactor struct {
 	stopped    uint32
 }
 
-func NewBlockchainReactor(store *BlockStore) *BlockchainReactor {
+func NewBlockchainReactor(state *sm.State, store *BlockStore) *BlockchainReactor {
+	if state.LastBlockHeight != store.Height() {
+		panic(Fmt("state (%v) and store (%v) height mismatch", state.LastBlockHeight, store.Height()))
+	}
 	requestsCh := make(chan BlockRequest, defaultChannelCapacity)
 	timeoutsCh := make(chan string, defaultChannelCapacity)
 	pool := NewBlockPool(
@@ -40,6 +51,7 @@ func NewBlockchainReactor(store *BlockStore) *BlockchainReactor {
 		timeoutsCh,
 	)
 	bcR := &BlockchainReactor{
+		state:      state,
 		store:      store,
 		pool:       pool,
 		requestsCh: requestsCh,
@@ -129,7 +141,11 @@ func (bcR *BlockchainReactor) Receive(chId byte, src *p2p.Peer, msgBytes []byte)
 	}
 }
 
+// Handle messages from the poolReactor telling the reactor what to do.
 func (bcR *BlockchainReactor) poolRoutine() {
+
+	trySyncTicker := time.NewTicker(trySyncIntervalMS * time.Millisecond)
+
 FOR_LOOP:
 	for {
 		select {
@@ -150,6 +166,48 @@ FOR_LOOP:
 			// Peer timed out.
 			peer := bcR.sw.Peers().Get(peerId)
 			bcR.sw.StopPeerForError(peer, errors.New("BlockchainReactor Timeout"))
+		case _ = <-trySyncTicker.C: // chan time
+			var lastValidatedBlock *types.Block
+		SYNC_LOOP:
+			for i := 0; i < 10; i++ {
+				// See if there are any blocks to sync.
+				first, second := bcR.pool.PeekTwoBlocks()
+				if first == nil || second == nil {
+					// We need both to sync the first block.
+					break SYNC_LOOP
+				}
+				firstParts := first.MakePartSet().Header()
+				// Finally, verify the first block using the second's validation.
+				err := bcR.state.BondedValidators.VerifyValidation(
+					first.Hash(), firstParts, first.Height, second.Validation)
+				if err != nil {
+					bcR.pool.RedoRequest(first.Height)
+					break SYNC_LOOP
+				} else {
+					bcR.pool.PopRequest()
+					err := bcR.state.AppendBlock(first, firstParts)
+					if err != nil {
+						// TODO This is bad, are we zombie?
+						panic(Fmt("Failed to process committed block: %v", err))
+					}
+					lastValidatedBlock = first
+				}
+			}
+			// We're done syncing for now (will do again shortly)
+			// See if we want to stop syncing and turn on the
+			// consensus reactor.
+			// TODO: use other heuristics too besides blocktime.
+			// It's not a security concern, as it only needs to happen
+			// upon node sync, and there's also a second (slower)
+			// method of syncing in the consensus reactor.
+			if lastValidatedBlock != nil && time.Now().Sub(lastValidatedBlock.Time) < stopSyncingDurationMinutes*time.Minute {
+				go func() {
+					bcR.sw.Reactor("BLOCKCHAIN").Stop()
+					bcR.sw.Reactor("CONSENSUS").Start(bcR.sw)
+				}()
+				break FOR_LOOP
+			}
+			continue FOR_LOOP
 		case <-bcR.quit:
 			break FOR_LOOP
 		}
diff --git a/consensus/reactor.go b/consensus/reactor.go
index 7abd75ec..bbc39c89 100644
--- a/consensus/reactor.go
+++ b/consensus/reactor.go
@@ -29,6 +29,8 @@ const (
 
 //-----------------------------------------------------------------------------
 
+// The reactor's underlying ConsensusState may change state at any time.
+// We atomically copy the RoundState struct before using it.
 type ConsensusReactor struct {
 	sw      *p2p.Switch
 	started uint32
diff --git a/consensus/state.go b/consensus/state.go
index ad8b79cf..e2738ca9 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -467,6 +467,8 @@ func (cs *ConsensusState) updateToState(state *sm.State) {
 	// Reset fields based on state.
 	validators := state.BondedValidators
 	height := state.LastBlockHeight + 1 // next desired block height
+
+	// RoundState fields
 	cs.Height = height
 	cs.Round = 0
 	cs.Step = RoundStepNewHeight
diff --git a/consensus/vote_set.go b/consensus/vote_set.go
index c640fc51..973d4b7a 100644
--- a/consensus/vote_set.go
+++ b/consensus/vote_set.go
@@ -34,7 +34,7 @@ type VoteSet struct {
 	maj23Exists   bool
 }
 
-// Constructs a new VoteSet struct used to accumulate votes for each round.
+// Constructs a new VoteSet struct used to accumulate votes for given height/round.
 func NewVoteSet(height uint, round uint, type_ byte, valSet *sm.ValidatorSet) *VoteSet {
 	if height == 0 {
 		panic("Cannot make VoteSet for height == 0, doesn't make sense.")
diff --git a/daemon/daemon.go b/daemon/daemon.go
index a4b573be..fae9c979 100644
--- a/daemon/daemon.go
+++ b/daemon/daemon.go
@@ -55,7 +55,7 @@ func NewNode() *Node {
 	pexReactor := p2p.NewPEXReactor(book)
 
 	// Get BlockchainReactor
-	bcReactor := bc.NewBlockchainReactor(blockStore)
+	bcReactor := bc.NewBlockchainReactor(state, blockStore)
 
 	// Get MempoolReactor
 	mempool := mempl.NewMempool(state.Copy())
@@ -70,10 +70,10 @@ func NewNode() *Node {
 
 	sw := p2p.NewSwitch()
 	sw.SetChainId(state.Hash(), config.App().GetString("Network"))
-	sw.AddReactor("PEX", pexReactor)
-	//sw.AddReactor("BLOCKCHAIN", bcReactor)
-	sw.AddReactor("MEMPOOL", mempoolReactor)
-	sw.AddReactor("CONSENSUS", consensusReactor)
+	sw.AddReactor("PEX", pexReactor).Start(sw)
+	sw.AddReactor("BLOCKCHAIN", bcReactor).Start(sw)
+	sw.AddReactor("MEMPOOL", mempoolReactor).Start(sw)
+	sw.AddReactor("CONSENSUS", consensusReactor) // Do not start yet.
 
 	return &Node{
 		sw:               sw,
diff --git a/p2p/peer_set.go b/p2p/peer_set.go
index 23f49c51..effad6dc 100644
--- a/p2p/peer_set.go
+++ b/p2p/peer_set.go
@@ -59,7 +59,12 @@ func (ps *PeerSet) Has(peerKey string) bool {
 func (ps *PeerSet) Get(peerKey string) *Peer {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
-	return ps.lookup[peerKey].peer
+	item, ok := ps.lookup[peerKey]
+	if ok {
+		return item.peer
+	} else {
+		return nil
+	}
 }
 
 func (ps *PeerSet) Remove(peer *Peer) {
diff --git a/state/validator_set.go b/state/validator_set.go
index 50f76f42..09589a9d 100644
--- a/state/validator_set.go
+++ b/state/validator_set.go
@@ -2,12 +2,15 @@ package state
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"sort"
 	"strings"
 
+	"github.com/tendermint/tendermint/account"
 	. "github.com/tendermint/tendermint/common"
 	"github.com/tendermint/tendermint/merkle"
+	"github.com/tendermint/tendermint/types"
 )
 
 // ValidatorSet represent a set of *Validator at a given height.
@@ -198,6 +201,50 @@ func (valSet *ValidatorSet) Iterate(fn func(index uint, val *Validator) bool) {
 	}
 }
 
+// Verify that +2/3 of the set had signed the given signBytes
+func (valSet *ValidatorSet) VerifyValidation(hash []byte, parts types.PartSetHeader, height uint, v *types.Validation) error {
+	if valSet.Size() != uint(len(v.Commits)) {
+		return errors.New(Fmt("Invalid validation -- wrong set size: %v vs %v",
+			valSet.Size(), len(v.Commits)))
+	}
+
+	talliedVotingPower := uint64(0)
+	seenValidators := map[string]struct{}{}
+
+	for idx, commit := range v.Commits {
+		// may be zero, in which case skip.
+		if commit.Signature.IsZero() {
+			continue
+		}
+		_, val := valSet.GetByIndex(uint(idx))
+		commitSignBytes := account.SignBytes(&types.Vote{
+			Height: height, Round: commit.Round, Type: types.VoteTypeCommit,
+			BlockHash:  hash,
+			BlockParts: parts,
+		})
+
+		// Validate
+		if _, seen := seenValidators[string(val.Address)]; seen {
+			return Errorf("Duplicate validator for commit %v for Validation %v", commit, v)
+		}
+
+		if !val.PubKey.VerifyBytes(commitSignBytes, commit.Signature) {
+			return Errorf("Invalid signature for commit %v for Validation %v", commit, v)
+		}
+
+		// Tally
+		seenValidators[string(val.Address)] = struct{}{}
+		talliedVotingPower += val.VotingPower
+	}
+
+	if talliedVotingPower > valSet.TotalVotingPower()*2/3 {
+		return nil
+	} else {
+		return Errorf("insufficient voting power %v, needed %v",
+			talliedVotingPower, (valSet.TotalVotingPower()*2/3 + 1))
+	}
+}
+
 func (valSet *ValidatorSet) String() string {
 	return valSet.StringIndented("")
 }
diff --git a/types/block.go b/types/block.go
index 11dfb3b9..176ce438 100644
--- a/types/block.go
+++ b/types/block.go
@@ -39,7 +39,9 @@ func (b *Block) ValidateBasic(lastBlockHeight uint, lastBlockHash []byte,
 	if !b.LastBlockParts.Equals(lastBlockParts) {
 		return errors.New("Wrong Block.Header.LastBlockParts")
 	}
-	/*	TODO: Determine bounds.
+	/*	TODO: Determine bounds
+		See blockchain/reactor "stopSyncingDurationMinutes"
+
 		if !b.Time.After(lastBlockTime) {
 			return errors.New("Invalid Block.Header.Time")
 		}