I remember people making some noise in the run-up to the 2004 elections about the breakdown of voters by education. Democrats considered it significant that folks with some postgrad study preferred Kerry 55/44/1. I don't blame them for trumpeting it, because whatever it means, it sounds great. Someone just brought it up again in another comments section.
The overall numbers: No Highschool Diploma split 50/49 for Bush. Not much for either side to cheer about there. HS Diploma 52/47 Bush; Some college, 54/46 Bush; College Grad 52/46/1 Bush/Kerry/Nader; Postgrad study, 55/44/1, Kerry/Bush/Nader, as above.
Since that time I ran across the statistic that just under one-third of those with some graduate school took Education. This puts a whole different light on the earlier statistic. Graduate students in Education have the lowest GRE's of any field of study. Their undergraduate GPA's in non-education courses were lowest in any field of study. Their SAT's were not only lower than those who went to graduate school in other subjects, they were lower than those who went on to no graduate school at all.
Advanced degrees in science correlate moderately well with intelligence measures. Other advanced degrees, less well. Grad school is more a measure of perseverence. Persistence is a good thing. It is probably a better quality to have than intelligence. But it is not the same thing.
Also, more than any other field (I am estimating), people in Education depend on government for employment. This would create a certain amount of self-interest in voting for parties that like federal funding of education. While it sometimes feels as if there's no longer any difference between Republicans and Democrats on that, that's just grouchiness on the part of deficit-hawk Republicans. There actually still is a difference. And as for perceptions, Democrats run way ahead of Republicans among educators. Classroom teachers run 61-39 Democrat. Education professors run 92-8 Democrat. Somewhere between that must be where those with some graduate study are. Call it 75-25 Democrat.
Now take those folks with graduate study in education out of the equation, because A) they're not as qualified (generally. Lots individuals with said degrees have superb intelligence), and B) they have a vested interest.
Well, Shazam! All of a sudden Bush is up again. 52/47/1. Huh. The moral of the story is, Kerry did best among people with no HS diploma plus people with some graduate study in Education.