Level of education is a pretty accurate indicator of intelligence. The cream generally rises to the top, if you will.
Just for fun, I looked up some data from a Pew Research Center study in Sept. 2016. I will use their education numbers for white voters, as almost all minority groups are heavily Democrat, regardless of level of education:
- White voters with HS diploma or less: 59-33, GOP
- White voters with some college but no degree: 57-36, GOP
- White voters with college degree plus: 48-47, Democrats