As California works the kinks out of its vaccine rollout and starts to reopen classrooms, it is tough to determine whether recall efforts will succeed. If the recall petitions qualify, voters would be asked two questions: Should Mr. Newsom be recalled, and if so, who should complete his term.

For now, fellow Democrats have closed ranks around Mr. Newsom, and the White House press secretary, Jen Psaki, emphasized this month that President Biden “clearly opposes any effort” to recall the governor.

When reporters recently asked about the recall effort, the governor said, “I’m focused on the vaccine issue.” His team, however, notes that recall attempts are not unusual in California: recall petitions have been filed against every governor in the last 61 years.

Already three Republicans — Kevin Faulconer, the former mayor of San Diego; the conservative activist Mike Cernovich; and John Cox, who lost to Mr. Newsom in 2018 — say they would challenge the governor, and Richard Grenell, acting intelligence chief under former President Donald Trump, would not rule it out.

The recall effort has also has tapped into a bipartisan unease as the virus’s death toll in California reached 50,000 lives on Wednesday.

In California, Republican registration has been falling for years. The party now represents less than a quarter of registered voters, but as Mr. Newsom has awkwardly constrained 40 million Californians in the name of safety, Republicans have sought to energize their base.

Harmeet Dhillon, a Republican national committeewoman and San Francisco lawyer, has peppered Mr. Newsom with pandemic-related lawsuits, filing on behalf of churches, and gun shops. Far-right groups have rallied against masks and business closures, and conservative sheriffs have refused to enforce state health rules.