Rep. Barney Frank, the first openly gay member of Congress, said Sunday he thinks President Obama's gay marriage endorsement will not sway anybody's vote. 

Though Washington is abuzz with speculation about how the president's historic statement in support of same-sex marriage will affect his reelection prospects, the Massachusetts Democrat said the announcement leaves the race more or less the same. 

"If you were going to cast your vote based on a candidate's position regarding same-sex marriage, you were already going to vote for Obama-Romney based on that," he said. "I literally don't think anybody's vote was changed by this one way or the other." 

Frank argued that the Obama administration already had pushed for the repeal of the "don't ask, don't tell" policy banning gays from serving openly in the military, and already had dropped its legal defense of the Defense of Marriage Act which defines marriage as between one man and one woman. 

"I can't think there are many people who said, OK, well, I'm going to vote for Obama even though he said that the Defense of Marriage Act is unconstitutional and he said gay people can serve in the military. But if he says marriage, that goes too far," Frank, who plans to retire at the end of his current term, said on ABC's "This Week." 

Conservatives, though, have said the announcement could hurt the president. Former GOP presidential candidate Rick Santorum called the issue a "potent weapon" for presumptive nominee Mitt Romney, should he choose to use it. 

Romney has since reiterated that he is opposed to same-sex marriage.