San Diego’s Republican mayor testified emotionally Tuesday about his transformation from a foe to a friend of same-sex marriage and spotlighted a central issue in the Proposition 8 case – whether the law can be based on prejudice against lesbians and gays if many supporters harbor no anti-gay bias.

With his daughter and her newlywed wife in the gallery, Jerry Sanders’ voice quavered as he described his turnabout in 2007 that led him to sign a City Council resolution supporting San Francisco’s lawsuit that sought marital rights for gays and lesbians. As a declared supporter of civil unions and an opponent of same-sex marriage, he had planned to veto the measure.

“I think the decisions I made were grounded in prejudice,” Sanders testified in federal court in San Francisco at the start of the second week of trial on the constitutionality of Prop. 8, the November 2008 ballot measure that limited marriage to opposite-sex couples. “I was discriminating even against my own daughter.”

Sanders said he witnessed similar discrimination in the 1970s, early in his 26-year career as a police officer, when he saw a gay sergeant driven off the force.

He said he felt “overwhelming love” as well as parental fears for his daughter Lisa, now 26, when she told him in 2003 that she was lesbian.

What tipped the scales in 2007, he said, was a meeting with gays and lesbians the day before his intended veto of the marriage resolution. They reminded him that they, too, had families with children, and “I was shocked at the depth of (their) hurt,” he said.

Read the rest of Bob Egelko’s San Francisco Chronicle article here.