I was disappointed in Romney's intellect in the last debate, when he got bogged down in a 15-18 minute pointless, petty squabble with McCain on the 'time lines' issue (who cares), with the endless 'he said, I said' ping-pong yelling match. That was ridiculous behavior from presidential candidates.
It seems Romney is prone to getting disoriented and tangled up in details, not exactly a presidential material. McCain is senile and seems to have been medicated to keep his temper in check. They're both waste of vote.
Mitt Romney may have been hoping to push McCain into meltdown mode. A logical strategy, though not necessarily one I would have recommended. Had he succeeded, people would have looked at McCain's melt down as "Of course the nice gentleman broke down--that mean rascal was tormenting him", rather than as "Good grief! If that flake can't even stand up to a debate, what's he going to do as President if a real crisis hits"?