As we’ve discussed before, the Republican party gets more support from the rich than from the poor, especially in poor states. (In poor states such as Mississipi, rich people are much more Republican than poor people; in rich states such as Connecticut, rich people are only slightly more Republican than the poor.)
Rich voter, poor voter
The next step is to look at time trends. Here we use the National Election Studies pooled into 20-year intervals. First, the difference between rich and poor voters in rich, middle-income, and poor states. As you can see, the gap in voting between rich and poor voters has increased, but especially in the poor states:
I don’t know exactly how this is related, but in the past 25 years, income inequality has actually been increasing faster in the rich states than the poor states.
Rich state, poor state
Next we look at things from the other direction, comparing the voting patterns of rich and poor states, but looking separately at rich, middle-income, and poor voters. As you can see, within each income category, there didn’t used to be any large systematic differences in voting patterns in rich and poor states until recently. Even now, the rich-state, poor-state difference shows up mostly among high-income voters, somewhat among middle-income voters, and not at all among the poor:
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.
P.S.: whites-only analysis
In response to some of the commenters below, I did an analysis with just whites (88% of the total dataset). Removing the minorities reduces the differences by about half. Here’s the new version of our first picture:
And here’s the second picture:
Among whites, the red-state, blue-state divide is still strongest among the rich but it’s no longer zero for the poor.