Audacious Epigone has crunched the numbers from the latest release of the ongoing General Social Survey to find out whose supporters in 2008 did better on the GSS's 10 word vocabulary quiz (the scores from which correlate surprisingly well with genuine IQ tests.
Posting vocabulary scores on an IQ scale, McCain voters scored 102.5 versus 99.9 for Obama voters. On a real IQ test, the gap might have been even larger because the GSS vocab quiz shows only about a 10 point W-B gap. I suspect that McCain did better than Obama among people with higher performance than verbal IQs. (I'm trying to think of anything in Obama's biography, a hobby or whatever, that suggests a knack for something not involving words, and I'm drawing a blank: when a state senator, he was good at winning at poker against lobbyists, so I guess we'll count that. McCain loves casino gambling, which is a lot dumber than playing poker with people with expense accounts for making you feel good.)
On the other hand, the kind of people who misremember whom they voted for probably tend to score badly, and Obama's number might suffer from a post-facto bandwagon effect among dopes.
Of course, what white people care about is the difference among white voters. And there Obama won, but very narrowly: 103.2 to 102.9.
All this fits in with a lot of exit poll data from elections over the last decade showing that years of education among supporters tend to be very similar between the Republican and Democratic candidates, while Republicans do better on income (and the effective gap is even larger because Democrats tend to live in high cost of living states).