Well exit polls did show that Obama won the 9% of people who decided in the last week by about 9 points IIRC. So a case could be made that those late deciders could have broken for Romney. However indications were that Obama had momentum starting after the 3rd debate.
As I predicted before the election, Sandy was going to enter GOP lore as the reason they lost their momentum just like the OBL tape is part of Dem lore for why Kerry lost his mo. In reality, both were likely on their way to defeat.
People who claim to have decided in the few days before the election almost always favor Democratic candidates more than the general population for whatever reason. I wouldn't take this to mean that Democrats actually win late deciders, just that Democrats are more likely to claim to be late deciders. (Personally, I think less than 1% actually decide in the last few days barring some enormous black swan event. People just like to claim to be undecided to pollsters, a kind of moderate heroism.)
