After years of equivocating on an issue that divides his country, President Barack Obama came out in favour of gay marriage in the US last night and suddenly injected an unpredictable social issue into a re-election campaign that had been expected to be fought on the economy.
Mr Obama's declaration was greeted with elation by gay rights campaigners who, just hours earlier, had been rocked by an overwhelming vote in North Carolina that amended the state constitution to bar same-sex marriages.
"It is important for me personally to go ahead and affirm that same-sex couples should be able to get married," the President said in a television interview, ending a long period in which he had frustrated many supporters by refusing to address the issue. He campaigned in 2008 on a platform in favour only of civil unions, and the White House has said since then that his position is "evolving".
Mr Obama said: "I have hesitated on gay marriage in part because I thought that civil unions would be sufficient. I was sensitive to the fact that for a lot of people the word 'marriage' was something that invokes very powerful traditions, religious beliefs and so forth."
There could be no more vivid demonstration of that than the vote in North Carolina on Tuesday, in which an uncompromising measure banning not just marriage but also civil unions passed by a 61 to 39 per cent margin.
All the so-called "Bible Belt" states in the south-eastern US have now taken similar steps; 29 US states have passed constitutional amendments barring same-sex marriage. However, gay rights campaigners have also taken many significant steps forward, amid polls that show support for same-sex marriage rising to about 50 per cent across the country with even higher figures among the youngest voters who overwhelmingly backed Mr Obama in 2008. Marriage licences are now issued to same-sex couples in six states and in Washington DC, while laws are pending to make them available in two more.
Mr Obama's stance puts a wedge between him and his Republican opponent, Mitt Romney, who said last night that he did not support same-sex marriage or civil unions.
What had seemed like a minor kerfuffle when Vice-President Joe Biden proclaimed himself "entirely comfortable" with gay marriage at the weekend, now seemed like part of a choreographed effort by the White House to energise the Democrat party base and to put Mr Obama on the right side of a civil rights issue that appears to be gaining momentum.
"President Obama's words today will be celebrated by generations to come," said Chad Griffin, president of the gay rights lobby group the Human Rights Campaign.
In North Carolina, campaigners vowed to fight to overturn the marriage ban. "We can't change the results of this vote, but we can determine what comes next," vowed Jasmine Beach-Ferrara, of the Campaign for Southern Equality.