Here's the "even" map of a generic Presidential election according to the Cook PVI, with "median" state (Colorado) in green.
Urban vs. Rural (population density)Hypothesis: The more rural, the more Republican.
% non-Hispanic white populationHypothesis: The more white, the more Republican.
Per-capita incomeHypothesis: The wealthier, the more Republican.
Median household incomeHypothesis: The wealthier, the more Republican.
Seems to me that urban vs. rural is the best predictor of voting patterns - whiteness has only a weak correlation and wealth appears to have a negative one (public-sector workers and urban vs. rural, presumably).
