A lot of variables that aren't always in play, some variables may interact in unforeseen ways.
Sure, incumbency is teh hawt. But they've sent out emails declaring that they will be outspent:
I will be the first president in modern history to be outspent in his re-election campaign, if things continue as they have so far.
I'm not just talking about the super PACs and anonymous outside groups -- I'm talking about the Romney campaign itself. Those outside groups just add even more to the underlying problem.
Sure, 94% of elections are won by the candidate that spends the most, but it's not (yet) money that is counted - it's votes by actual people.
Sure, there have been a number of voter suppression schemes put in place, but then again there are millions of people pissed off about how badly they've been economically cornholed recently.
Sure, more people will get to the polls, but it's not a popular vote, it's an electoral college.
Sure, swing states mean more than safe red/blues... But the same way a general rise in sea temp allows storms to form outside of the normal 'storm track', the general rise in voter attention allows electoral storms to form outside of the normal 'swing state' track - meaning we may have new swing states just like in 08.
Lots of not-run-of-the-mill shit going on this time around. Hell, it was a shocker that a conservative on the scotus acted in a manner that seems to respect rule of law. It's almost bizarro world out there.