The always interesting Andrew Gelman, Rich state, poor state, red-state, blue-state: it’s all about the rich:
Thus, the familiar “red America, blue America” pattern, the “culture war” between red and blue states, is really something happening at the higher range of incomes.
I believe that the details of history are always driven by battles between the elites….
Update: zeil asks if this is a race effect. From Rich State, Poor State, Red State, Blue State: What’s the Matter with Connecticut?:
Could the varying income effects we have shown be merely a proxy for race? This is a potentially plausible story. Perhaps the high slope in Mississippi reflects poor black Democrats and rich white Republicans, while Connecticut’s flatter slope arises from its more racially homogeneous population. To test this, we replicate our analysis, dropping all Africanâ€“American respondents. This reduces our key pattern by about half. For example, in a replication of Figure 5, the slopes for income remain higher in poor states than in rich states, but these slopes now go from about 0.2 to 0 rather than from 0.4 to 0.
To see if the income patterns could be explained by other demographic variables, we went back to the full dataset for the Annenberg surveys in 2000 and 2004 and added individual-level predictors for female, black, four age categories, and four education categories; and group-level predictors for percent black and average education in each state. After controlling for all these, the patterns for income remained: within states, the coefficient for individual income on probability of Republican vote was positive, with steeper slopes in poorer states; after controlling for the individual and group-level predictors, richer states supported the Democrats.