Sen. Barbara Boxer asked embattled San Diego Mayor Bob Filner to step down "immediately" Friday, after at least 12 women came forward in recent weeks to accuse him of sexual harassment, including two veterans.
Boxer had already joined a growing chorus of California officeholders to publicly call for Filner to quit, but in Friday's letter, she asked him directly.
"Bob, you must resign because you have betrayed the trust of the women you have victimized, the San Diegans you represent and the people you have worked with throughout your decades in public life," Boxer wrote.
Filner, a 70-year-old Democrat, represented the San Diego area in Congress for 20 years before he was elected mayor in November.
Filner had served as chairman of the Veterans Affairs Committee in the House of Representatives and had even introduced legislation to protect women in the military from sexual harassment. But this week, two female veterans accused him of the very behavior he'd spoken out against.
A series of shocking sexual assault and harassment cases in the armed forces recently moved Boxer and several of her colleagues to introduce legislation to make it easier for victims to come forward and for their attackers to be prosecuted.
Last month, Filner apologized for his behavior, saying he'd "diminished" his office and said he'd seek therapy.
"You have every right to be disappointed in me," he said in a statement. "I only ask that you give me an opportunity to prove I am capable of change, so that the vision I have for our city's future can be realized."
But Boxer said that wasn't good enough.
"To avoid hurting your victims and the people of San Diego more than you already have, you should step down immediately," she wrote Friday.
Sen. Dianne Feinstein, D-Calif., last month asked Filner to quit.
Rep. Nancy Pelosi, D-San Francisco, however, has not. Nor has Gov. Jerry Brown, who endorsed Filner to lead California's second-largest city and campaigned for him last year.
Boxer has been a staunch advocate on behalf of women who faced sexual harassment. As a member of the House, she pushed for Senate hearings on allegations against Supreme Court nominee Clarence Thomas.
In the Senate, she pushed for punishment of Navy commanders after the Tailhook scandal. Later, one of her own colleagues, Sen. Bob Packwood, R-Ore., resigned after she pushed for an investigation into sexual harassment accusations against him.
However, when President Bill Clinton stood accused, Boxer did not ask him to resign.
Read Boxer's letter to Filner.
PHOTO: San Diego Mayor Bob Filner pauses during a news conference at San Diego City Hall on July 26, 2013. The Associated Press/ Gregory Bull