The Republican mayor of San Diego — the last remaining large city in California with a conservative base — changed his position on gay marriage last week:

A tearful Mayor Jerry Sanders made a dramatic shift yesterday, explaining that he can no longer oppose same-sex marriages because he does not want to deny justice to people like his daughter, who is a lesbian.

Joined at a late afternoon news conference by his wife, Rana Sampson, the San Diego mayor announced he will back a City Council decision to support same-sex marriage before the state Supreme Court, where California’s ban on it awaits review.

“I decided to lead with my heart, which is probably obvious at the moment,” said Sanders, moments before he revealed his daughter’s sexual orientation.

The mayor’s new stance marked a reversal of his pledge Tuesday to use his veto power to block the council’s move. At the time, he repeated his preference for civil unions, partnerships between same-sex couples that offer some but not all of the legal protections given to those who marry.

Describing what led to his decision, Sanders referred to friends and staffers who are gay, as well as his daughter:

“In the end, I couldn’t look any of them in the face and tell them that their relationships, their very lives, were any less meaningful than the marriage I share with my wife, Rana,” said Sanders, who quickly thanked reporters and dashed from the room.

San Diego has a population of 1.26 million, and is the second largest city in California and the eighth largest city in the United States. It is home to a large population of military retirees, which explains its large number of Republican voters, but it has a sizable gay community, as well:

Nearly 62,000 San Diegans are part of households led by a same-sex couple, according to a U.S. Census Bureau survey conducted two years ago.

Sanders is a former police chief who won a hard-fought election two years ago in the wake of multiple GOP scandals in San Diego County, including bribery charges against Rep. Duke Cunningham and a sleazy case in which the acting mayor and a city council member, both Republicans, were sent to prison for conspiring to ease restrictions on strip clubs.

Sanders’ principled position stands in stark contrast with Vice Pres. Dick Cheney, who also has a gay daughter, but who has won election based in no small part on an anti-gay agenda.

With new elections underway, Sanders’ change of heart may well cost him the election but, unlike the vice president, he will leave office with his his personal integrity intact.