The residents of Oakland, Calif., were already frustrated. Violent crime and burglaries had become enough of a problem that getting an In-N-Out burger and fueling up near the airport was considered a risky endeavor.

The city’s last remaining major league sports team announced in April that it would leave town after 57 seasons. And the population, currently 425,000, has been in decline since the coronavirus pandemic.

All of which served to drive signatures for a recall election against Mayor Sheng Thao only 18 months into her tenure — a rare ouster attempt in a city this large.

Then, two days after the recall qualified for the ballot last week, F.B.I. agents raided the home of Ms. Thao and stayed there for hours.

Before they scoured Ms. Thao’s house in the Oakland hills, it was possible, even likely, that she would survive the recall election this fall with the help of the same progressive allies and labor unions who supported her mayoral campaign in 2022, longtime political hands in the Bay Area said. But the raid has now cast a shadow over her future, even as she defiantly vowed on Monday to fight for her political survival.

“Everybody understands that she hasn’t been charged with a crime,” said Brenda Harbin-Forte, a retired Alameda County Superior Court judge who is a main organizer of the recall. “But our focus is that you can’t lead a city and be distracted about whether any day now you’re going to get indicted for a federal crime.”