Just a side note: Obama was winning NH for an entire 3 days before the election.
Personally, I think the 8-10% "undecided" are actually people who voted for Bush the second time and don't want to admit it to a pollster or an Obama canvaser knocking at their door. Especially in a swing state. Every single ad is for a politician in those places. They're REALLY sick of the election and being asked what or who they're voting for. In fact, some of them will make stuff up on purpose. No, really.
Bottom line: In an election year that's defied conventional wisdom time and again, remember that anything can happen.