President Barack Obama has changed his position and now unequivocally supports the legalization of same-sex marriage. 

“I’ve just concluded that for me personally it is important for me to go ahead and affirm that I think same sex couples should be able to get married,” Obama said in an interview with Robin Roberts of ABC News on Wednesday.

The president had previously said his position on same-sex marriage was "evolving," which rankled many of his supporters. At a New York gala with LGBT supporters last June, Obama said that "traditionally, marriage has been decided by the states,” which prompted jeers from the crowd.

Obama is the first sitting president to back the legalization of same-sex marriage. The move comes a day after voters in the swing state of North Carolina resoundingly backed an amendment to ban gay marriage. 

"I think it is a move that is not without risk for Obama and the Democrats," said Patrick Egan, a political scientist at NYU who has studied gay marriage voting trends. "It's not clear to me that he gains more votes than he loses by taking this position. My sense is the margin is small either way." 

The real boost, Egan said, may be in fundraising. "My sense is that you're going to see a lot of gay donors who were reluctant to open their wallets to be much more friendly towards supporting the Obama campaign in the fall."

The president will be cultivating that support in another New York fundraiser on Monday afternoon. The reception, scheduled to be held at the Rubin Museum and hosted by Ricky Martin, is targeting both Latino and LGBT donors. 

President Obama's policy shift followed Vice President Joe Biden’s comment on Meet the Press on Sunday that he was “comfortable” with same-sex marriage. Education Secretary Arne Duncan followed a day later with similar sentiments. Housing and Urban Development Secretary Shaun Donovan, a New Yorker, was the first cabinet member to voice support for legalizing gay marriage last November. 

Democratic New York Sen. Kirsten Gillibrand, who has championing the repealing the Defense of Marriage Act, said the president’s backing of same-sex marriage will mean a fresh look at the legislation.

“Having the president at the helm will make an enormous difference in our call for equality,” Gillibrand told WNYC.

She said Obama’s decision to support same-sex marriage is “instrumental” to ensuring marriage equality.

“It gives us such an opportunity to now look at this legislation, hopefully in a new light, and galvanize the support that we need to repeal the Defense of Marriage Act,” she said.

Following the broadcast of the president's remarks, Republican presidential nominee Mitt Romney reaffirmed his opposition to legally recognizing same-sex marriage at a campaign stop in Oklahoma City. Romney called the issue "a very tender and sensitive topic," but said he has been consistent that the legal definition of marriage should be restricted to one man and one woman. 

But some opponents of same-sex marriage say the president's move means Romney needs to take a stronger position. "If Romney says well, 'I think marriage should be between a man and woman,' and does not support a constitutional amendment, he will have conservatives walk away from him," Bill Donahue of the Catholic League told WNYC. "He has to either man up now the way the president has and finally say what's on his mind or he has to risk the presidency on this." 

WNYC's Brigid Bergin and the Associated Press contributed reporting.