In a telephone interview yesterday, Villaraigosa described a lengthy courtship by both Clintons, starting with a phone call from Hillary Clinton on the January morning when she announced her presidential candidacy.

The mayor also recalled conversations with her at his Los Angeles home and at his office; two private dinners in Washington; and several phone conversations. He also said he spoke with Bill Clinton for 45 minutes about an endorsement, and that he and the former president were working together on a project to reduce global warming. The two men also had dinner at the Kobe Club in Manhattan this month, he said.

"From that first morning, I talked to her and heard from her more than any other candidate in the race," said Villaraigosa.

For several of the Democratic candidates, the Villaraigosa endorsement was pursued as a huge political prize, which it may turn out to be. The California presidential primary has taken on new importance with its move to Feb. 5 from June. Villaraigosa, the mayor since 2005, has a network of supporters as mayor of the nation's second-largest city and as a former speaker of the state Assembly, and he is widely seen as a rising star in the party and a national spokesman on Hispanic concerns like immigration and education.

"I think that Mayor Villaraigosa is truly a national political star, and we're grateful to have his support," said Patti Solis Doyle, Hillary Clinton's campaign manager. (According to two California Democrats, Solis Doyle, the first Hispanic woman to steer a presidential campaign, courted the mayor aggressively, sometimes talking to him or his aides once a week.)

The endorsement will enable Villaraigosa to build more political and fundraising connections around California and the nation as he prepares for a widely expected run for governor in 2010, political analysts said.

The mayor said other presidential candidates who had sought his endorsement, in meetings or phone conversations were Obama, Richardson, John Edwards, the former North Carolina senator, and Sens. Christopher J. Dodd and Joseph R. Biden Jr., of Connecticut and Delaware, respectively

"This is the deepest and most talented field of Democratic presidential hopefuls in recent memory," Villaraigosa said, "but Hillary has demonstrated a strength and an experience that I think sets her apart."

The mayor denied that ethnic pride was ever a factor or a concern as he weighed possibly endorsing Richardson.

"I know Bill Richardson quite well," the mayor said, "and I think I'll say his strength is his experience and his record, not his ethnicity. I love the guy. I know him. He would say his strength is his resume."

Richardson kicked off his campaign in Los Angeles this month, speaking in English and Spanish and overtly appealing to the ethnic pride of Hispanics. Villaraigosa said he met with Richardson around that time.

Asked if the endorsement spelled trouble for the Richardson campaign, a spokesman for the governor said Richardson was confident he would win the California primary without the mayor's support.

"Governor Richardson is more interested in getting the support of Latino voters rather than big-name Latino leaders," said the spokesman Pahl Shipley. "He has never felt that high-profile endorsements help much in a campaign."