Two hours later, Telemundo television anchor Mirthala Salinas delivered the story to her Spanish-language viewers on the Friday evening news.
What Salinas, 35, did not say in the newscast was that she was the other woman. She and Villaraigosa, 54, had been in a relationship even though she had previously been the political reporter assigned to cover local politics and the mayor.
On Tuesday, prompted by a report in the Daily News of Los Angeles, Villaraigosa officially confirmed what had long been whispered around City Hall.
"I have a relationship with Ms. Salinas, and I take full responsibility for my actions," he said at a news conference after a swearing-in ceremony for school board members at the Dorothy Chandler Pavilion downtown.
By late afternoon, the Channel 52 anchor had issued her own confirmation.
"I first got to know the mayor at a professional level, where we went on to become friends," she said. "The current relationship grew out of our existing friendship."
Salinas said that although she and the mayor "are both public figures, I hope that everyone can understand and respect my desire to maintain my privacy when it comes to personal relationships."
Villaraigosa's admission cast a fresh shadow over his own personal conduct: He has two adult daughters born out of wedlock and his wife filed for divorce in 1994 over a separate affair for which he later publicly apologized. They eventually reconciled.
It may also have damaged his carefully crafted image as a family man, something he has reinforced over the years by appearing with his family in campaign literature and -- until this week -- on the city's website. And it is unclear how the political fallout will treat one of the region's most recognizable figures.
The revelation also raised ethical questions about Salinas' decision to become involved with a politician she was covering as a journalist. Several media analysts condemned the relationship as a conflict for her and the mayor and suggested that Salinas' bosses should have taken immediate action to remove her from handling any Villaraigosa coverage.
"There really is no question that this is unacceptable," said Kelly McBride, ethics group leader at the Poynter Institute in St. Petersburg, Fla. "You can't sleep with your sources. This one sort of transcends the boundaries in any ethical newsroom."
Telemundo executives defended Salinas and noted that she had been moved in August 2006 from her political beat to cover general assignment stories and serve as a backup anchor.
"Mirthala Salinas is one of our most respected reporters and a great professional," said Manuel Abud, Telemundo's general manager in Los Angeles. "Telemundo is fully committed to journalistic excellence. Every day we strive for the highest standards of journalistic ethics and make every effort to protect our objectivity and avoid possible conflicts of interest."
Villaraigosa, who called Salinas a "consummate journalistic professional," said she decided about a year ago that "our friendship had grown to a point where it was necessary to inform her management that she shouldn't cover me. She did that. And they agreed."
The Times traced their relationship back at least 18 months.
In November 2005 -- four months after he was sworn into office -- Villaraigosa was seen one evening by a resident of the Sherman Oaks condominium complex where Salinas lived at the time.
Jean Rouda recalled pulling into the garage about 9 p.m. and seeing Villaraigosa standing alone and buzzing to get into the building. Rouda said she recognized the mayor and was surprised that he had no security guards and that there was no limousine parked nearby. She said she and her niece entered the lobby, where they encountered Villaraigosa, who was wearing a dress shirt and slacks, and was carrying bags of takeout food and a bottle of wine.
The two women and Villaraigosa got into the elevator. He extended his hand to Rouda and introduced himself as Antonio.
"I look at him and go, 'I know who you are. I know who you're going to see. Tell her I say hi,' " she recalled.
Rouda said she was certain that Villaraigosa was visiting Salinas because everyone else in the 15-unit complex was "older and Jewish" except for her. "I knew he was not going to visit an elderly Jewish woman with wine and food," she said.
Rouda, a self-described news junkie, said she recalled the chance encounter because it was the night before the funeral of Rosa Parks in Detroit, which she saw reported on television and noticed that Villaraigosa had attended. Rouda said that at the time, she chose not to tell anyone about meeting the mayor because she thought it was a private matter. She spoke only after Times reporters contacted her recently.
Salinas subsequently moved to another condo in Studio City. In the meantime, Villaraigosa and Salinas crossed paths professionally over the next year.
On March 20, 2006, Salinas was in New York to cover Villaraigosa, who was visiting Mayor Michael Bloomberg to discuss education reform.
Three months later, she went to Sacramento to cover Villaraigosa as he stumped for legislation to give him some control over Los Angeles' public schools. Salinas covered a news conference and appears alongside the mayor in pictures taken by a Times photographer. One of the photographs was published in the newspaper and caught the attention of Villaraigosa's staff, who knew of their building relationship and privately worried that word of the affair might leak out.
Then in September 2006, Villaraigosa played a direct role in the medical care of Salinas' mother, Yolanda Avila Fernandez, who was being treated for cancer at Cedars-Sinai Medical Center, according to sources familiar with her case. The mayor consulted with doctors on a regular basis and appeared in Fernandez's hospital room with her family on the eighth floor of the complex's north tower, serving as an emotional anchor and an unofficial spokesman for Salinas and her siblings.
Fernandez was eventually transferred to USC/Norris Comprehensive Cancer Center east of downtown, where a doctor described the mayor as "a model citizen."
Fernandez died Jan. 4. Two days later, Villaraigosa flew to Phoenix to attend weekend memorial services for her at the Greer-Wilson Funeral Home.
"He did come for services," said Eddie Lopez, the funeral home's general manager. "I remember him being there."
All along, Villaraigosa and his aides remained silent about the relationship.
Then in late January, rumors about the Villaraigosas' shaky marriage escalated after a local Internet blog reported that the mayor and his wife had separated.
In an interview with The Times, Villaraigosa denied the report, which was fueled by the fact that he had stopped wearing his wedding ring, a point cited in the blog item. Aides said Villaraigosa, who had lost weight, stopped wearing the ring because it was slipping off. He was wearing it during the interview.
The last time Villaraigosa spoke publicly about his personal life was June 11, when he held a news conference to talk about the split with Corina Villaraigosa. At the time, he would say only that he felt a "personal sense of failure" about the breakup and hoped everyone would respect his family's privacy. The next day, she filed for divorce.
But speculation continued to build about Salinas, whose name and picture appeared on Internet blogs, along with allegations that she was pregnant.
Asked Tuesday whether Salinas is pregnant, Villaraigosa said: "I can tell you emphatically that that question is outrageous and the answer is no, she is not pregnant."
Villaraigosa is not the first politician to be linked to Salinas. Assembly Speaker Fabian Nunez, (D-Los Angeles), confirmed in a recent interview that he dated Salinas in 2003 when he was divorced from his wife; the two have since reunited. Nunez is a longtime Villaraigosa friend and political ally.
Salinas has worked as a radio and television journalist in Los Angeles and Phoenix for more than 13 years, according to her Telemundo biography.
She covered the political beat until she disclosed her relationship with the mayor. Her duties were then expanded to include general assignment stories and working as a backup anchor, according to a statement from the station and company spokesman Alfredo Richard.
She has been filling in as the anchor on the 6 p.m. news for the last few months while the regular anchor, Lucia Navarro, is on maternity leave.
Salinas did not anchor the broadcast Tuesday night but did appear in file footage in Telemundo's report on her relationship with Villaraigosa.
Laura Castaneda, an associate professor of professional practice for the USC Annenberg School of Journalism, criticized Telemundo for allowing Salinas to report on the mayor in any respect, saying it was "completely inappropriate" for the station to let Salinas announce the mayor's breakup with his wife.
"I think Telemundo is going to have to really take a hard look at this," said Castaneda, who has conducted research about Spanish-language media. " It doesn't reflect well. Telemundo has no excuse."
On Tuesday, most members of the City Council either declined to comment on Villaraigosa's confirmation or said that it was his own business.
That contrasted with hundreds of readers who left comments on The Times' website, with some agreeing that it was a private matter while others arguing that it showed a lack of integrity.
"He has no right to privacy in this matter as he already made a public spectacle of his family values on many occasions," one reader wrote.
Another reader posted the opposite.
"I don't care who he sleeps with, I care how he runs the city."
Times staff writers Hector Becerra, Anna Gorman and Sam Quinones and researcher John Tyrrell contributed to this report.