SAN FRANCISCO — A giant rainbow-colored flag in the gay-friendly Castro neighborhood here was flying at half-staff on Wednesday as social and religious conservatives celebrated passage of measures to ban same-sex marriage in California, Florida and Arizona.

In California, where same-sex weddings had been performed since June, the ban passed with 52 percent of the vote, according to figures by the secretary of state and projections by several California media outlets. Opponents of same-sex marriage won by even bigger margins in Arizona and Florida. Just two years ago, Arizona rejected a similar ban.

The across-the-board sweep, coupled with passage of a measure in Arkansas intended to bar gay men and women from adopting children, marked a stunning victory for religious conservatives, who had little else to celebrate on an Election Day that saw Sen. John McCain lose his presidential race and other ballot measures, such as efforts to restrict abortion in South Dakota, California and Colorado, rejected.

"It was a great victory," said the Rev. James Garlow, senior pastor of Skyline Church in San Diego County and a leader of the campaign to pass the California measure, Proposition 8. "We saw the people just rise up."

The losses devastated supporters of same-sex marriage and ignited a debate about whether the movement to expand the rights of same-sex couples had hit a cultural brick wall, even as another civil rights milestone — the election of a black president — had occurred. Thirty states have now passed bans on same-sex marriage.

Supporters of same-sex marriage in California, where the fight on Tuesday was fiercest, appeared to have been outflanked by the measure's well-organized backers and, exit polls indicated, hurt by the large turnout among black and Hispanic voters drawn to Sen. Barack Obama's presidential candidacy. Obama opposes same-sex marriage.

California will still allow same-sex civil unions, but that is not an option in Arizona and Florida. Exit polls in California found that 70 percent of black voters voted for the ban. Slightly more than a majority of Latino voters, who made up almost 20 percent of voters, favored the ban, while 53 percent of whites opposed it.

Proposition 8 was one of the most expensive ballot measures ever waged, with combined spending of more than $75 million. Focus on the Family and other religious conservative groups contributed funding to the help pass the gay marriage measures in all three states.