(CBS News) WASHINGTON - President Obama revealed Wednesday that he now supports same-sex marriage, becoming the first U.S. president to take that position.
It was a dramatic moment, felt around the country - and it's sure to affect his campaign for re-election.
It was met with applause and outrage.
It's being called a landmark moment for equality - and also a political flip-flop.
Mr. Obama announced the stand in an interview with ABC News, saying, "It is important for me to go ahead and affirm that I think same-sex couples should be able to get married."
"I had already made a decision that we were going to take this position before the election and before the (Democratic) convention," the president added.
White House officials tell CBS News Vice President Biden's endorsement over the weekend pushed up Mr. Obama's timing.
Asked in the interview if he was upset with Biden for jumping the gun, Mr. Obama said Biden "got out a little bit over his skis, but out of generosity of spirit."
"Would I have preferred to have done this in my own way, in my own terms, without, I think, there being a a lot of notice to everybody? Sure. But all's well that ends well."
Still, White House officials are privately making no secret of their annoyance with Biden because, they say, it forced the president's hand to make the announcement this week.
And a senior White House official repeated to CBS News that Biden's remarks on "Meet the Press" Sunday were not an intentional trial balloon on the subject of same-sex marriage.
Mr. Obama's change of heart on the issue has come only gradually.
In 2008, he went on record opposing same-sex unions, saying, "I believe that marriage is the union between one man and one woman."
More recently, Mr. Obama said his feelings were constantly evolving.
In a December 2010 news conference, he told reporters, "This is something we're going to continue to debate and I, personally, am going to continue to wrestle with going forward."
The White House stresses this is a personal decision for the president. He believes the federal government has no role - that the question of same-sex marriage should be left to the states.
But nothing is quite so simple in an election year, and the president's change of heart could complicate his re-election effort.
He stressed Wednesday that, unlike the president, he has not changed his mind.
"I have the same view on marriage that I had when I was governor (of Massachusetts)," Romney said, "and that I've expressed many times. I believe marriage is a relationship between a man and a woman."
And while the president's advisers admit they don't know for sure how the announcement will play out politically, Republicans, such as Christian conservative activist Ralph Reed, say the decision will help Romney raise money from small donors and recruit volunteers.
"I think what this does is it gives the Romney campaign an unanticipated gift-wrapped present as we go into the general election," Reed says.
Popular support for gay unions has increased in recent years. The country is now split on the issue.
But 38 states have laws defining marriage as between one man and one woman, including several important swing states.
Larry Sabato, of the University of Virginia, says that, in the end, same-sex marriage won't decide the election.
"This is mainly an election about the economy," Sabato observes, "but there will be pluses for President Obama in Democratic blue states and minuses in Republican red states. It may be a wash overall, but there are political impacts."
In his book, "The Audacity of Hope," Mr. Obama writes that he worries about being on the wrong side of history when it came to same-sex marriage.
His announcement also comes in advance of his trip to Hollywood Thursday night for a major fundraiser yet - the campaign expects the gala at the home of George Clooney to raise $14 million.