A year ago this week, President Obama folded himself into a chair in the White House Cabinet Room to make an announcement that had no impact on federal law or policy -- but one that was filled with emotional meaning for the president and many of his strongest supporters.
"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," the president told ABC News' Robin Roberts in an interview last May 9.
The president chose his initial words carefully -- "me personally," he said -- in a small reflection of his continuing unease, and the slightly awkward circumstances of his announcement.
The president was completing a self-described personal "evolution" on gay marriage that was hardly surprising, particularly under the immediate public pressure provided courtesy of his own vice president.
Yet the announcement managed to course through politics and society in ways that were impossible to fathom at the time. A year later, the politics of the issue have flipped almost completely, to the point where supporters of same-sex marriage are playing offense, not defense.
Beyond the electoral battlefield, the president's decision ushered in a year of lightning-fast movement on gay rights, with the impact felt in realms including the Boy Scouts, professional sports, and the Supreme Court.
"It, quite simply, changed everything," said Richard Socarides, a former Clinton White House senior adviser who had been critical of Obama's hesitancy on gay-rights issues. "So much is dramatically different just a year later. It really shows the power of the presidency and the power of a presidential endorsement, especially in the very personal and moving way that this president did it."
Last fall, statewide ballot measures for the first time legalized gay marriage, with four states moving in unison on one day. Eleven states now allow gay marriage, with Rhode Island joining the list last week and Delaware coming on Tuesday. A handful more are shifting quickly in that direction.
Nearly six in 10 Americans now believe gay marriage should be legal, a boost of 26 points inside a decade, according to a recent ABC News/Washington Post poll. That number jumps to eight in 10 among those under 30, charting a future course of seeming inevitability.
All but three Democratic senators now support gay marriage, and two Republicans in the Senate do as well. It's now difficult to imagine any Democrat challenging for the presidency holding the same anti-gay marriage position that every serious candidate held through the 2008 campaign.
Later this month, the Boy Scouts of America will consider whether to drop its longstanding ban on gay participants. Just last week, the first active player in a major American male team came out as gay -- an African-American basketball player whom Obama approvingly noted "can bang with Shaq."
Opponents of gay marriage aren't giving up the fight -- but neither are they denying the momentum, or the president's role in generating it.
"Has it had an effect? Yeah, absolutely," said Tony Perkins, president of the Family Research Council and a leading voice against gay marriage. "He's used the bully pulpit to advance a redefinition of marriage."
But Perkins noted that 30 states still have gay-marriage bans on the books. He said those in favor of gay marriage will soon run out of states where legalizing it will be easy, and predicted a public-opinion backlash as the full implications of expanded gay marriage are felt.
"You look at the scoreboard, it's 30-10," Perkins said. "We're clearly far from a tipping point as a nation…. And the fallout from this will become more and more evident. It's not just about the marriage altar. It's about fundamentally altering our society.
"I'm not saying all the cultural trends are positive. I'm just saying it's too early to call the game," he added.
It's easy to forget, in the flurry of events and rapid shift in public opinion, that the president's announcement was a bombshell at the time.
Obama's reelection campaign was just getting under way. His positioning against Republican Mitt Romney focused on economic issues far more than social ones. Many Democrats with knowledge going back two election cycles shuddered at the thought of flip-flopping to support gay marriage.
"It may hurt me," the president told Robin Roberts, fretting openly about the impact in battleground states.
Another piece of important context: Vice President Joe Biden had made Obama's opposition to gay marriage -- something many of his liberal supporters long refused to believe was genuine -- a sudden flashpoint.
Days before Obama's statement, Biden shocked his own West Wing by pronouncing himself "absolutely comfortable" with gay and lesbian couples getting married, putting daylight between the president and his vice president.
Privately, according to White House aides, Obama had decided to announce his support for gay marriage months before Biden spoke out, and was looking only for the appropriate time and forum. Biden's public prodding forced the issue, and Obama chose a presidential interview to drop the news.
It was a move greeted with uncertainty at Obama campaign headquarters in Chicago.
"We didn't have a clear view about whether there would be an impact among certain demographics," said Ben LaBolt, who was the Obama campaign's press secretary.
With the benefit of a year's hindsight, such concerns were unfounded. There was no purple-state backlash. The Obama campaign credits the announcement with energizing the Democratic base, starting with gay-rights activists who were anxious for action and found a new, big reason to work hard for the president's reelection.
"In the gay community, there was never a question about overwhelming support. But the intensity level shot up in an enormous way," LaBolt said.
Obama himself has evolved even further in the past year. His administration jumped into the Supreme Court fight against California's gay-marriage ban, and the president told ABC News' George Stephanopoulos in March that he couldn't see a constitutional justification for states to deny same-sex couples the right to get married.
His position has gained currency much faster among Democrats than Republicans. Gay marriage counts a handful of supporters among Republicans, including high-profile names such as Sen. Rob Portman, R-Ohio, and former Vice President Dick Cheney, but most Republican elected officials -- and the party base -- oppose gay marriage.
Some Obama backers hope last year's announcement provides something of a leadership model for the president in his second term.
"The way to win, and to be successful as a president, is to take principled stands, use political capital to fight for them, and go out and say what you believe," Socarides said.
At the time, many gay-rights activists thought Obama too slow to come around on the issue. It appeared, at the time, that Biden forced his hand.
Yet in Obama's wake, other public officials have rushed to support gay marriage, edged along by a public that's more accepting of the concept, said Fred Sainz, a spokesman for the Human Rights Campaign, a gay-rights organization.
"The water was warm, so he could go ahead and weigh in," Sainz said. "He laid a runway -- a glide path for a number of issues that might not have happened without his having coming out for marriage equality."