Focus on Virginia. Ohio is a swing state that could go either way with every election, but Virginia is one of those "blue" states we can actually put into the Democratic (or lean-Democratic) column. The Democrats can lose Ohio and probably still win, but if the Republicans start losing southern states, they'd have to take most everything else to pull off a victory. Or at least a narrow one.
Of course, putting North Carolina in play and campaigning there (like having the convention in Charlotte) would probably have some effect on Virginia just because it's a neighboring state. If North Carolina doesn't go GOP, neither will the election.
This is plausible, IMO. Unlikely, but plausible with the Democratic convention in NC. I call it the creative class strategy gone wrong:
FL is the true clincher for Obama. The scenarios where the Republican wins with Florida going for Obama are even more ridiculous. For the Republican candidate, I think the clincher state is CO. Obama can, barely, win without PA if he takes VA and FL. The stats seem to argue in favor of the VA strategy on the whole.
Eh. I'm not too sure about Wisconsin and Pennsylvania going Republican with North Carolina and Virginia going Democrat.
Colorado will most likely stay Democrat in 2012. It's gotten very liberal over the years.