Something to note here. Per CNN's exit poll, 10% of voters decided presidential candidate to vote for in the last week of the election, including 3% over the weekend and 4% on Election Day itself.
Standard caveat regarding MOE, and there appears (maybe) to be a smaller undecided vote (i.e. a more stratified electorate) than in 08, but lets not discount the real possiblity of undecideds breaking strongly for Romney (or against Obama) over the weekend being enough to push Mitt over the top.
Mind you, that's what Romney absolutely needs at this point to win; even a mere "respectable, but not heavy" majority of undecideds going for Romney this week might flip CO and FL, but ultimately still means four more years.
Undecideds don't necessarily break against the incumbent. They went 57-41 for Bush in 2004 IIRC.
