President Obama has said he supports same-sex marriage—a move that will change no law, at least immediately, but that represents a watershed moment in the recognition of LGBT Americans as full and equal citizens.

The statement came in a television interview with ABC News and it came at a pivotal political moment, less than 24 hours after North Carolina voters overwhelmingly approved a constitutional amendment banning not just same-sex marriage but also civil unions. Obama was careful to present his statement as one of personal belief: He’s not proposing to make same-sex marriage rights a national crusade. But he also left no ambiguity about his sentiments. "I think same-sex couples should be able to get married." This is a huge development. As Greg Sargent observes, "Obama has become the first — and only — sitting president to come out for full equality for gay and lesbian Americans."

During the interview, Obama indicated that his position on gay marriage had evolved. He's talked about this his evolving views before—for example, in response to a question from progressive blogger Joe Sudbay at a 2010 White House roundtable. I have no idea if his views really shifted or whether, as many have speculated, Obama quietly believed in same-sex marriage all along. But the idea that Obama’s views changed, at least incrementally, is not so far-fetched.

Today’s New York Times noted the proliferation of television shows featuring same-sex couples, many of them with children, and the lack of protest they have produced. I suspect that’s not simply because the shows happen to be appealing or because they’ve become so commonplace. I think it’s also because, like Obama, so many Americans have come to know gay and lesbian couples personally.

I've seen that on a personal level, as the attitudes of friends and relatives have changed. I can see it most vividly in my children, who have friends with gay or lesbian parents and seem totally oblivious to it. No, not everybody in every place feels this way. Not even close. But more people in more places feel this way than ever before.

That doesn’t necessarily mean Obama will benefit politically, although it's possible he will. (My colleague Noam Scheiber offers one reason why.) Polls show that a majority of Americans now support gay marriage, but polls don’t measure intensity or predict how voters will react once national political figures focus on an issue. A fair reading of today’s statement is that Obama just told the voters of North Carolina, a toss-up state he very much hopes to win in 2012, that they are wrong. That's at least a little brave—or, if you're a strategist for his campaign, a little risky. 

But whatever happens in the next few months, the long-term trend is clear. Acceptance of same-sex marriage is rising, as my colleague Nathan Pippenger notes. And it is rising faster than virtually anybody anticipated.

Someday same-sex marriage will seem as natural to most Americans as racially integrated lunch counters. Particularly if that moment comes soon, history may remember Obama's statement less for moving public opinion than for reinforcing a move that was already underway. That's fine. It's still a huge development—one we should applaud and celebrate.

Update: For a particularly moving and eloquent reaction, I highly recommend reading Andrew Sullivan, who has played no small part in advancing the cause of marriage equality:

I think of all the gay kids out there who now know they have their president on their side. I think of Maurice Sendak, who just died, whose decades-long relationship was never given the respect it deserved. I think of the centuries and decades in which gay people found it impossible to believe that marriage and inclusion in their own families was possible for them, so crushed were they by the weight of social and religious pressure. I think of all those in the plague years shut out of hospital rooms, thrown out of apartments, written out of wills, treated like human garbage because they loved another human being. I think of Frank Kameny. I think of the gay parents who now feel their president is behind their sacrifices and their love for their children.

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