Well, let's ponder how many people in 1968 voted one way or the other because of the events of WWII. After all, that was was a lot closer (about 1/2) to '68, then '68 was to '08 (easily more important also). The only real 'historical' vote goes on within the party faithful who will vote for their party, or not vote - as was the case last time with the 'Pubs who saw massively poor turnout in a lot of places because McCain was seen as as MeTooBushII person, and a RINO.
That Reagan would win, hell, "Generic Republican" beats Obama in every poll, tragically they have to nominate a real person and that's when it hits the skids. You'd have a hard time finding three people who are harder to like than old frothy, Rick Santorum (whose honorary chair in Florida is quoted this morning as saying "gays 'make god want to vomit'", Mitt (who's taking the gloves off now, well just as soon as his butler does it for him), and Newt one the most consistently unlikable people in American politics (and that's no small feat).
Added to that, you're going to have a huge union factor (and thanks to CU they too can spend unlimited cash) in 3 critical swing states, Wisconsin, Ohio and Indiana. And one thing that unions have that PACs don't is the ability to turn out lots of people, not only for the election, but also for the campaign work.
You've got a highly polarized and clearly split electorate, but two factors seem to help the Dems. One that their basic demographics skew lower in age, (which means more Dems than R's over the long run as the Tea Party types tend to die off). Second is that states themselves are becoming more red or blue as time goes on. And it's the richer, more educated states (those with an industrial base) that are going more blue, and the poorer ag states that sink deeper into the red. And though there is a nation-wide two-party system, on local levels its' becoming much less that way. And when you have to toss the two largest electoral states (California and New York) as highly-unlikely to ever go red, then you need to run the table on the rest.
The single biggest problem that Obama faces is one of the easiest to deal with - that he hasn't unified the country at all. And where that might be an issue in normal times (and should be) in fact it won't be any sort of issue at all. Because the GOP can't campaign against that without admitting they're part of the problem.
Add to that, folks could consider voting for Mitt, but they will never vote Newt. But If Mittens wins the nomination, he will be Palin'd. The GOP will force him to take Santorum or one of those as his running mate to appeal to the base, and that will scare the moderates away. An electable GOP candidate doesn't appeal to the nutjobs, and a nutjob scares away the middle 40%. It's kind of hilarious.