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."