Annise Parker's mayoral campaign Web site bio reads like a catalog of campaign catchphrases: She has been Houston's city controller and a member of City Council. She's for job creation, against irresponsible spending and tough on crime.

Until the last line: "Annise Parker and her life partner, Kathy Hubbard, have been together since 1990. They have two children."

Parker, 53, has never made a secret or an issue of being a lesbian. Not during her bid to be Houston's next mayor nor in previous campaigns.

But others have. If Parker wins the Dec. 12 runoff election, Houston would become what's believed to be the largest U.S. city ever to have an openly gay mayor _ and that has catapulted Parker's sexual orientation into the center of the race.

Anti-gay activists and conservative religious groups have endorsed her opponent, former city attorney Gene Locke, and sent out mailers condemning Parker's "homosexual behavior."

Meanwhile, gay and lesbian political organizations nationwide have endorsed Parker, raised money for her and plan to run phone banks rallying her supporters.

The controversy has put Locke in a precarious political position. With the election expected to be tight, the 61-year-old has been trying to distance himself from anti-gay attacks while courting conservative voters who could tip the race in his favor. If Locke wins, he would be Houston's second black mayor.

Two of Locke's key supporters contributed money to a conservative political action committee that sent out an anti-gay mailer earlier this month urging voters not to pick Parker because she was endorsed by the "gay and lesbian political caucus." Campaign finance reports show Ned Holmes, finance chairman of Locke's campaign, and James Dannenbaum, a member of the campaign's finance committee, each gave $20,000.

"Gene is disappointed and wishes that Ned Holmes had not made that contribution. Gene has been very clear with his supporters to not participate in divisive campaigning," Kim Devlin, a senior Locke adviser said in a statement Tuesday. "Gene Locke has fought against bigotry his entire life and knows that there is no place for it in this campaign and this city."

Parker's campaign said she did not want to be interviewed by The Associated Press on the issue.

The dynamics of the mayoral runoff echo California's Proposition 8 vote in 2008, where black voters formed an unusual alliance with conservatives to approve a measure that banned same-sex marriage, said Richard Murray, a University of Houston political scientist.