Last week, when it was asserted in the NY Times that "Democrats do as well among top earners as Republicans," MediaMatters got its panties all in a twist over apparantly contradictory exit polling data from the 2006 and 2004 elections. Since, in my experience (contrary to the stereotype of rich Republicans), wealthy suburbs are generally fairly left-leaning, I was surprised to find such a substantial Republican advantage in exit polls for those with incomes over $200,000 given that America is very nearly split down the middle between parties so a 30-point gap is substantial. The $100,000 number is, I think, not particularly helpful since, if 20 percent of all households earn at least that much, it hardly illuminates the behavior of the wealthiest voters.
The $200,000+ disparity is particularly strange given the current edge Democrats have in campaign fundraising. Of course, it's possible that the few extremely wealthy donors account for a disproportionate amount of donation money, or that self-reported exit polling is not the most accurate way to determine the relationship between income and voting. (Or, as my econ professor would probably point out, income statistics do not appropriately account for wealth.)
However, a quick comparison of 2006 returns in the wealthiest zip codes shows a seemingly smaller partisan gap. In New York and California, these districts voted pretty much in favor of incumbents of either party (Clinton carried the ultra-rich in NY, and Schwarzenegger and Feinstein in CA), but in open races, the Democrats seemed to have a slight, but probably insignificant, edge. For example, Eliot Spitzer won the majority of gubernatorial votes in every wealthy district in NY. The richest zips in Nevada and Arizona tended Republican--in keeping with a regional tendency. In fact, the wealthiest zip codes frequently returned conflicting candidates to the House, Senate, and Governor's mansion. Compared to my home district, which elects Democrats to every single public office, these districts were shockingly balanced. Of course, this is all highly unscientific number-plugging into CNN's vote tracker, and it doesn't reveal any data about returns for local races. Still, it does seem as though, at the top of the income scale, where owning a $2 million home is a reality, the partisan gap is pretty small.
This evidence has been noted elsewhere, but the only explanation for it I've seen so far is that (Democratic) poorer people in wealthy areas have higher voter turnout than the (Republican) super-rich, thereby tipping the district in favor of Democrats. This is possible, but I wonder where these poor people are hiding in districts where the median home price is $700,000 and there are, by all accounts, very few rental properties, no less cheap ones.
UPDATE: Cheryl sends along this from the Atlantic, which includes a link to this study showing a closing partisan gap among wealthy voters.