A victory for Carl DeMaio, who is locked in a tight mayoral race, would make San Diego the second-largest city in the US to elect an openly gay mayor and the largest to elect a gay Republican.
Yet perhaps no group has opposed DeMaio as loudly as the city's sizeable gay and lesbian population.
Angered by his reticence on gay issues and his acceptance of campaign donations from backers of Proposition 8, California's 2008 ban on same-sex marriage, parts of the crowd booed DeMaio at a mayoral debate at the gay and lesbian community centre. He was booed again as he walked hand in hand with his partner in this year's gay pride parade.
And many gay and lesbian leaders have lined up behind Bob Filner, 70, a Democratic congressman and DeMaio's opponent in the November 6 election.
"For Carl DeMaio to be elected mayor would not be a victory for gay and lesbian people," said Linda Perine, a longtime lesbian organiser. "It would be a defeat."
That DeMaio, 38, could become the next mayor of San Diego - long a conservative outpost in liberal California - offers more evidence of just how dramatically the political landscape has changed for gays and lesbians. But this race has also exposed the challenges gay Republicans running for office still face as they try to balance a desire to further gay rights against an appeal to conservatives who oppose gay marriage.
While that list of gays and lesbians running for public office has grown in recent years — Houston elected a lesbian mayor, Annise Parker, in 2009, and Tammy Baldwin is challenging in Wisconsin to become the first openly gay US senator - few have been Republican.
In part, Filner, a former Freedom Rider and outspoken advocate of gay rights, owes his wide support from gay voters to simple partisan politics: gays and lesbians across the country vote overwhelmingly for Democrats.
DeMaio said it was only a small minority among gay voters, with ties to organised labour, that so vocally opposed him.
But the Gay & Lesbian Victory Fund, which supports openly gay candidates from both parties, did not endorse DeMaio; neither did the Log Cabin Republicans, the party's leading gay political group, which is supporting Mitt Romney for president.
"I'm proud of San Diego that sexual orientation has not played an issue in this race," DeMaio said. "I've been running on fiscal reforms. That's the agenda that has brought so many diverse groups together."