Candidates and their supporters have aired political ads more than 1.3 million times since the start of 2025, according to data from advertising researcher AdImpact.
Benjamin Fanjoy/For the S.F. Chronicle
Tom Steyer and Matt Mahan are running on housing and education. Eric Swalwell and Antonio Villaraigosa are running against Donald Trump.
The candidates for California governor are spending millions of dollars on ads to define themselves against these issues — and more.
Candidates and their supporters have aired political ads more than 1.3 million times since the start of 2025, according to data from advertising researcher AdImpact. The Chronicle analyzed data from those ads to determine how much money each campaign has spent on blanketing airwaves and streaming services, and which topics come up most often.
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Billionaire and former hedge fund manager Tom Steyer has poured by far the most money, most of it from his own pocket, into advertisements. As of April 9, he’d spent roughly $89 million on more than 1 million ad airings, becoming a regular feature in Californians’ commercial breaks and social media feeds. The ads had drawn about 2.9 billion views among people ages 35 and above, according to AdImpact’s estimate.
Steyer’s campaign has been so expansive that he’s spent more than $1 million on ads that, by AdImpact’s measure, reached zero people. Almost all of those ads aired around midnight.
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Other candidates’ ad spending similarly matched the size of their campaign funds. San Jose Mayor Matt Mahan, and a few third-party groups backing his campaign, spent about $12 million on airings, while Rep. Eric Swalwell — whose campaign is now in doubt among allegations of sexual assault — spent more than $5 million.
Some candidates, including former U.S. Rep. Katie Porter and former state Controller Betty Yee, have spent much less money on advertising, though the data doesn’t include the videos they’ve posted to their own social media accounts. Conservative commentator Steve Hilton spent less than $500 on a series of social media videos, according to the data. Fellow Republican and Riverside County Sheriff Chad Bianco recorded no ads.
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Because Steyer has run by far the most advertisements, the issues he brings up — including housing and utility costs — dominate the candidates’ overall screen time. But pro-Mahan ads also often center on housing. In fact, 43% of all candidates’ ads that aired between the start of 2025 and April 9, 2026, mentioned the topic.
AdImpact’s data only includes up to three issues mentioned in an ad, meaning some topics may go uncounted if the ad references more issues than that.
Still, there are some general patterns in the issues some candidates return to. Yee and Porter, for example, have been more likely than other candidates to criticize lobbying and special interest influence. Swalwell, former Los Angeles Mayor Antonio Villaraigosa and former California Attorney General Xavier Becerra have put opposition to Trump at the forefront of many of their videos.
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What’s not included in the table above are the ads run by “California is Not for Sale,” one of the few committees so far that have organized entirely in opposition to a candidate. The group, which is mostly funded by the California Association of Realtors, has spent roughly $1.8 million on attack ads against Steyer.
Some of the candidates have thrown a few punches, too. Steyer has spent roughly $1.5 million on airings of an ad attacking Swalwell, while Villaraigosa has spent a much smaller sum — about $17,000 — on Spanish-language ads criticizing Becerra.