PORTLAND — After admitting he lied to cover up a sexual affair with a young man, the gay mayor of a major city with a reputation for liberal politics is about to find out how tolerant his constituents really are.

Portland Mayor Sam Adams admitted this week he lied to cover up his relationship with Beau Breedlove because a potential mayoral candidate had spread rumors that Adams had sex with a minor.

Adams says he lied because he was afraid voters wouldn’t believe that his young lover had turned 18 before they started having sex.

Adams was 42 and Breedlove a 17-year-old legislative intern when they met in 2005. Both say their relationship did not become sexual until after Breedlove turned 18, the legal age of consent as an adult.

Barraged with criticism, the potential candidate didn’t run, and Adams won election. He took office on New Year’s Day, making Portland the largest U.S. city with an openly gay mayor.

Less than three weeks later, Adams made a public apology and said he would resign if staying was not in the city’s best interest.

On Wednesday, three Portland newspapers and the city police union called for his resignation, while Oregon Attorney General John Kroger agreed to an investigation.

One of the newspapers is Just Out, which serves the gay and lesbian community.

“By his own admission, by committing the act of lying to the citizens of Portland, Adams has failed to show the principled character that this publication feels is a basic requirement for an elected official,” Publisher Marty Davis and the editorial board said in a statement.

The county district attorney, Michael Schrunk, and Portland Police Chief Rosie Sizer asked Kroger to investigate.

“Right now one of the big things we in government need is credibility with the public,” Schrunk told The Oregonian, another newspaper calling for Adams to resign. Sizer said it would be inappropriate for her department to investigate the mayor.

But unless Adams bows to pressure and resigns, or there is evidence of a crime, he will remain in office for the first half of 2009 because state law bars any mayoral recall until after six months.

“As far as we can tell there is no crime, so it becomes an issue of violating the public trust rather than any set of rules,” said Jim Moore, a Pacific University political science professor.

The key to his political survival, Moore said, is whether the four Portland city commissioners support Adams, because they will respond to public concerns.

Three have expressed disappointment but were otherwise supportive, while the fourth has not talked about the admission so far.

Commissioner Nick Fish said the commissioners met Wednesday and joined the request for an investigation by the attorney general. But they decided to withhold comment until that investigation is completed.

“This is clearly a distraction, but people need to know we are getting work done,” Fish said.

Moore said that former Mayor Vera Katz faced several recalls, but she was a very effective mayor with the support of the commissioners. Adams gained prominence as her chief of staff, and then won a City Council seat.

But Moore said that former Mayor Tom Potter, whom Adams succeeded, was effectively isolated by the commissioners during his final months in office.

“If we see that kind of isolation, we’ll know that Sam is on thin ice and will have to think about how effective he can be and whether to stay on the job,” Moore said.