YouGov has been tracking approval of President Obama on the issue of gay rights since 2009. Below is a chart that shows how Obama approval on gay rights has changed since he took office. Importantly, the last data point on the chart is from May 5-7, before the President officially announced his support of same-sex marriage.
For the majority of Americans, gay rights are far from being the most important issue in American politics. So it's likely that respondents' overall view of Obama have had some influence on their approval of his performance on the issue of gay marriage. Still, the sudden uptick in Obama disapproval on the issue over the last several weeks is more prominent than the recent change in overall Obama approval, shown here:
Democrats in particular had started to turn on Obama on the issue of gay rights in the last few weeks. We can see that here:
