In Red State, Blue State, we talked about how, in recent years, the Democrats have been winning the rich states, even while richer voters lean Republican.
What happened in 2008? Exit polls were made available immediately--as of election night. The next step is to go to individual-level data, which we recently obtained from the Pew Research Center's pre-election polls.
Here's the income and voting pattern at the national level:
Republicans did better among upper-income voters--except possibly for the over-200,000's. (The highest income category from the Pew surveys is "$150,000+", so we can't do a direct comparison at the top.)
Red and blue states
Now let's look at red, blue, and purple states (which we define, following our book, as those states where George W. Bush won by more than 10 points in both his campaigns, those where he lost by more than 10 points both time, and the states in between):
As in previous elections, income predicts Republican vote more strongly in red than in blue states. (For this and following graphs, I'm switching the x-axis from numerical incomes to income categories.)
Or, to put it another way, the red-state/blue-state divide is happening among the rich (actually, the upper middle class, since surveys don't tell us much about the truly rich) more than the poor.
The next step is to look at the states one by one. First, I'll compress each state to a single number, defined as the difference between McCain's vote share among Americans with incomes over $75,000, minus his vote share among those with incomes below $40,000. (I think these represent family incomes, and I choose these particular cutpoints so as to get approximately a third of survey respondents in each category.)
Here are the raw data, for stability restricting ourselves to the 38 states for which the sample size was at least 200 in the Pew surveys:
As before, the difference between rich and poor is largest within poorer, more Republican states. (Patterns from exit polls are similar but not identical; for these purposes, I prefer the Pew polls because they were less of a rush job and had more time to try to get a representative sample.)
Whites and blacks
But . . . is this all simply explained by race? In poor states such as Mississippi, low-income voters are likely to be African-American, and so the rich-poor divide is also a white-black divide. In rich states such as Connecticut, not so much.
We can check easily by restricting ourselves to the 76% of survey respondents who declare themselves white (and not Hispanic):
Individual states have moved--see Misssippi--but the overall pattern remains.
What's the matter with Connecticut?
The dramatic graph that got us started was the "superplot" of voting vs. income in the poorest state (Mississsippi), a middle-income state (Ohio), and the richest state (Connecticut). We can estimate the pattern of income and voting within each of these states using multilevel modeling, and here is the result:
(You don't want to know the effort that went into making this graph. I started by setting up a model for vote given state and income, then I shifted each state to correct for differences between the poll-based estimate and the actual election outcome in each state.)
I was all prepared to find big changes since 2004--but the detailed analysis of income and voting appears to show that the differences between rich and poor in different states are about the same as before. Obama's victory represented a national partisan swing rather than a redrawing of the electoral map.
Here are the time trends.