Pew's latest (pdf):
The partisan breakdown:
About half of Republicans (53%) say they feel less favorably toward Obama because of his support for gay marriage. By contrast, 60% of independents and 52% of Democrats say their view of Obama has not changed. Among independents, as many say they feel less favorably as more favorably toward Obama as a result of his gay marriage decision (19% each). Far more Democrats say they feel more favorably than less favorably toward Obama (32% vs. 13%).
TNC points out that black voters aren't running scared. Ruy Teixeira sees no political downside for Obama:
Hispanics are also not a plausible candidate for significant desertions based on the issue. They are not even particularly conservative on marriage equality: In the latest NBC/Wall Street Journal poll, 55 percent supported marriage equality compared to 49 percent overall. We should not expect to see many Hispanics abandoning Obama simply on this issue and embracing his opponent, Mitt Romney, who holds hugely unpopular positions on immigration, an issue of far more importance to these voters.
The Dish 