I saw something on the internet recently that showed a really direct correlation between the average IQ of a state and their voting preference in the 2004 election. I followed up to try to understand where the data came from. I couldn't find any reliable source data in 20 minutes or so of searching, so I thought I would do my own thing.
I went to the US Government Census website, pulled off median family income by state from the 2000 Census and compared that to the percent voting for Kerry. It came up with a correlation of 0.53. You can see on the chart that there is quite a bit of scatter in the data. However, when you put that on a table sorted and color coded it is more impressive. Higher income correlates pretty well with Kerry voters.
What does that mean though? I'm tempted to say that there is a correlation between education and income, therefore smarter people tend to vote Kerry, but there are probably a lot of holes in that argument. In any case, follow the link and make your own judgments. At least it is real data.