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.