But Republican strategists and gay rights activists said on Thursday that the issue’s power as a political tool for Republican candidates is diminishing. While surveys suggest that Americans are evenly divided on whether the federal government should recognize gay marriages, opposition has fallen from nearly 70 percent in 1996.

Prominent Republicans like Dick Cheney, the former vice president, and Barbara Bush, daughter of the former president, have defended the right of gays to marry. And Mr. Obama has been emboldened by the largely positive response to his recent, and successful, push for Congress to repeal “don’t ask, don’t tell,” the military’s ban on gays serving openly.

At the same time, the rise of the Tea Party movement, and the success that Republicans had last year in attacking Democratic candidates on economic issues, has pushed the debate over abortion and gay rights to the back burner.

“I don’t think this is the issue that it once was,” said John Feehery, a Republican strategist. “I think that the economic issues are so big that this one pales in comparison.”

In his first two years in office, Mr. Obama drew criticism from gay rights advocates who thought he was dragging his feet on their issues. Those same advocates see the shift as evidence that with an eye on the 2012 campaign, the president has calculated that the benefits of responding to his base outweigh the risks of upsetting conservatives who wouldn’t be voting for him anyway.

Among them is John Aravosis, the founder of Americablog.com, who in a 2009 blog post called the administration’s first legal brief in a Defense of Marriage Act case “despicable” and “homophobic.” Mr. Aravosis said on Thursday he is “much happier” with Mr. Obama, adding: “I think the gay community got to him. I’m not convinced we got to his heart, but I think we got to his political head.”