SAN FRANCISCO — Former House Speaker Nancy Pelosi has endorsed San Francisco Supervisor Dean Preston, a progressive lightning rod, as he faces a tough reelection challenge in a local race that has drawn the attention of other national figures from Elon Musk to Bernie Sanders.

The endorsement comes as Preston, a member of the Democratic Socialists of America, has faced an onslaught of attacks from political advocacy groups, bankrolled by tech investors, who are critical of his opposition to tough-on-crime policies. Those groups are spending heavily to back Bilal Mahmood, a moderate Democrat, tech entrepreneur and former Obama administration staffer.

Last fall, Preston gained national attention after billionaire provocateur Musk called for his imprisonment for supporting an ordinance to prohibit security guards from using firearms to prevent theft. Musk also suggested he would spend $100,000 to defeat Preston. It’s unclear if he has spent any money on the race.

Pelosi’s camp exclusively confirmed to POLITICO that she has endorsed Preston and will vote for him Wednesday night, when the County Democratic Party’s central committee makes its picks in local races. San Francisco’s supervisors are equivalent to city council members, shaping local policy and the budget. The post has long been a launching pad for the state’s political up-and-comers who’ve risen to greater prominence, including the late Sen. Dianne Feinstein, Gov. Gavin Newsom and state Sen. Scott Wiener.

“This is a powerful endorsement from one of San Francisco’s most powerful leaders, and I look forward to working with Speaker Emerita Pelosi in our united effort to defeat Donald Trump,” Preston said in a statement.

Preston represents a deeply liberal district that includes the Haight Ashbury, Fillmore, Japantown, Hayes Valley and Tenderloin neighborhoods. His other opponents in the November election include activists Autumn Looijen and Allen Jones.

Pelosi, generally a moderate Democrat by San Francisco standards, has a long pattern of endorsing incumbents from both the party’s more progressive and centrist wings.

It’s a balancing act Pelosi has continued even as moderate-backed candidates have swept a host of local races by seizing on voters’ frustrations over homeless encampments, record drug overdose deaths and rampant retail theft. Mahmood — Preston’s main challenger — is part of a slate of moderate Democrats who recently won control of the county party.

Nevertheless, Pelosi’s endorsement is a stinging rebuke for moderate groups who’ve spent heavily to try to defeat Preston and support Mahmood.

The supervisor’s race could provide a bellwether for political observers watching if San Francisco’s pivot to the right continues. In the March primary, voters passed several tough-on-crime measures, including a proposal to require drug screening for local welfare recipients.

Mahmood has disavowed Musk and said he hasn’t received any money from him in the race. He has tried to portray himself as a more pragmatic Democrat.

Musk, who recently vowed to move some of his companies’ operations out of San Francisco, posted on X last fall that Preston “should go to prison.”

Preston has called Musk a “billionaire fascist” and vowed to no longer use X, the billionaire’s company formerly known as Twitter. Soon after, Vermont Sen. Sanders, a fellow Democratic socialist, endorsed Preston and urged progressives across the country to support him.