Progressive Candidate Could Upend the San Francisco Mayor’s Race

The contest has been dominated by Mayor London Breed and her moderate challengers. Supervisor Aaron Peskin seeks to change that.

San Francisco residents have repeatedly told pollsters they don’t support Mayor London Breed. But until now, every one of her challengers in the November election has sounded a lot like her.

They have talked about adding police officers and taking a tough-on-crime approach to the drug and mental health crises on the city’s streets. They have tried to appeal to frustrated voters who recalled school board members and the city’s prosecutor two years ago, then expanded police powers and restricted welfare benefits last month.

But as those mayoral contenders try to outmaneuver one another from the middle, they may have left an opening for a candidate on the left. Into that void has stepped Aaron Peskin, president of the San Francisco Board of Supervisors.

Mr. Peskin, 59, confirmed in an interview that he will file papers on Friday to run for mayor. While other rivals thought Ms. Breed might be ousted by someone to her right, Mr. Peskin could win the race if enough liberals coalesce around him in a city known for its left-wing politics.

Mr. Peskin said this week that he agrees with the other candidates that the San Francisco Police Department needs more officers, and he would try to create a program to seek recruits from local colleges. He said he also agrees that fentanyl dealers must be arrested and jailed.

But unlike some of his rivals, he does not believe police should crack down on public drug use. He also said Ms. Breed had not done enough to expand treatment options for those addicted to drugs, and he opposed her successful measure on the March ballot to require welfare recipients to undergo drug screening.