actually, I think you're underestimating how god-awful Romney is in person. Based on some of the accounts I've read his gaffes have been under-reported in the media, and these aren't cute George W. Bush "Is our children learning?" type gaffes, but real callous insult type stuff.
he's gone from telling bakers in a donut shop that he could probably get better baked goods "at a 7-11" to telling a roomful of unemployed people that he understands them because he's unemployed now too. The guy just can't help himself.
I do think one factor which you sort of touched on is something I agree with: the animosity which a number of voters hold against Bush & the GOP for the years 2001-2009 is still strong enough that it will influence this election; I mean, voters elected Obama to fix everything that Bush or his political appointees fucked up, and Obama hasn't... if a "dangerous socialist" like Obama is too far to the right, what is Romney going to be? I'm guessing a lot of voters who are otherwise unhappy with Obama don't want to find out, and therefore will swallow hard and stick with the status quo.
and that's why I keep coming back to Romney himself; the GOP could've seriously threatened Obama if they had gone with a guy who wasn't "Richie Rich and proud of it" during a time when the vast majority of the country is getting squeezed by stagnant wages and benefits & persistent high unemployment.
and while most people aren't economists and are pretty stupid, I think the cries from the right-wing noise machine about socialism and "dangerous government holding business back" are starting to ring hollow by this point. cutting social spending, regulations, and taxes has been going on since the 80s, and things aren't getting better for them. Quite the contrary. And listening to a guy like Romney tell you to pull yourself up by the bootstraps isn't inspiring anymore, it's infuriating to voters. They fell for that shit in the 80s... but you can't fool all the people all the time...