As just about everybody knows by now, richer Americans tend to vote Republican while poorer Americans go for the Democrats.
But this isn't true for all groups. For an amusing example that we discussed in our book, a survey found that richer journalists were more likely to identify as Democrats (a fact which I'm sure will not surprise Michael Barone).
To look at this more thoroughly, Dan Lee and I took the 2000 and 2004 Annenberg surveys and looked at a bunch of different categories of people, classified by self-identified political ideology (very conservative to very liberal), religion (Catholic, Protestant, etc.), church attendance, age, ethnicity, sex, marital status, urban/suburban/rural, education, and attitude on abortion (just as an example of an opinion question).
Dan made this graph which shows the difference in support for the Republican candidate for president, comparing voters in the upper and lower third of income, looking separately at each of a bunch of different slices of the population. At the top of the graph are the people who self-identify as conservative: among this group the rich are about 25% more Republican than the poor. At the bottom are liberals, for whom the rich are slightly more likely to vote for Democrats. Here's everybody:
(Click on any of these graphs to see larger versions.)
A striking pattern. The differences between rich and poor are much larger among conservative, Republican groups than among liberal, Democratic groups. At the very bottom of the graph above, you see a few groups where richer people are more likely to vote Democratic. All of these are groups that are mostly liberal and Democratic.
To look at it another way, we made a graph showing the different subsets, plotting rich-poor voting differences vs. average Republican vote for the group. Separate graphs for 2000 and 2004:
Pretty consistent, I'd say. Now we have to think about what this all means.
P.S. In the lower graphs, the x-axis is the Republican-ness of the group (as measured by % favoring the Republican candidate for President, minus % favoring the Democratic candidate for President), compared to the U.S. average. The y-axis is the difference in Republican vote preference, comparing people in each group who are in the top third of U.S. family income, comparing to those in the bottom third. "Rich" and "poor" are defined here based on the national income distribution, not using separate income levels by subgroup. And we're looking at vote preference (from pre-election polls), not actual votes. We're using the Annenberg pre-election surveys, which is what we used for a lot of our analyses in Red State, Blue State.