Maine voters today repealed a state law that would have allowed gay couples to marry.
With 87% % of the precincts reporting, those against same-sex marriage had 53% of the vote.
The outcome represents a significant defeat for the gay rights movement, particularly because it happened in a north-eastern New England state – the corner of the country most supportive of gay marriage.
A "people's veto" of a law passed this spring, which made Maine the sixth state to extend marriage to same-sex couples, was on the ballot.
The law was put on hold after conservatives launched a petition calling for it to be repealed in a referendum.
"The institution of marriage has been preserved in Maine and across the nation," Frank Schubert, the chief organiser, said.
Supporters of gay marriage supporters had held out hope that the tide would shift but eventually conceded defeat.
"We're in this for the long haul," Jesse Connolly, the manager of the pro-gay marriage campaign, said. "For next week, and next month, and next year – until all Maine families are treated equally.
"Because in the end, this has always been about love and family, and that will always be something worth fighting for."
The Maine vote against same-sex marriage will encourage opponents who say American voters do not want to allow it. A vote in favour would have been the first time same-sex marriage had been approved at the ballot.
Of the five others to have allowed same-sex marriage, four are in New England.
Connecticut, Iowa, Massachusetts, Vermont and New Hampshire allow same-sex couples to marry. In those states, same-sex marriage was either enacted by the legislature or through judicial action.
In contrast, voters have approved gay marriage bans in every state –31 –in which they have reached the ballot, a statistic same-sex marriage opponents say shows that Americans want to keep the institution of marriage between a man and a woman.
In a similar vote in California last year, voters narrowly approved a constitutional amendment to restrict marriage to a man and a woman, overturning a judicial decision.
The Maine governor, John Baldacci, a Democrat, signed the same-sex marriage law in May, and opposed the repeal.
Money and volunteers streamed into the state on both sides of the fight. Same-sex marriage backers led by a group called Protect Maine Equality raised $4m (£2.4m), while $2.5m was raised by Stand for Marriage Maine, a major backer of the repeal vote, according to the Associated Press.
