Brin's $102 Million Fails to Bury California's Billionaire Tax

Silicon Valley billionaires have poured more than $379.5 million into stopping Proposition 40, a one-time 5% tax on California billionaires that voters decide in next week's midterms — the most expensive opposition campaign in state history. Google co-founder Sergey Brin alone has contributed at least $102 million through the Super Pac Building a Better California, more than any other donor, campaign finance filings show.

Prop 40 would tax billionaires living in California as of 1 January 2026, with proceeds funding healthcare programs plus some education and food assistance. It traces back to Donald Trump's One Big Beautiful Bill Act, signed on 4 July, which cuts roughly a trillion dollars of Medicaid, Affordable Care Act and other healthcare funding over a decade. When the bill takes effect in January, more than 3.4 million Californians could lose coverage, including millions of children.

"That's why we were willing to do something that lots of people said was crazy," said Dave Regan, president of SEIU-United Healthcare Workers West and the measure's architect. "To us, what's crazy is doing nothing and watching millions of people lose coverage."

How much money is flying?

In the first two weeks of October, the opposition spent more than $42.8 million — over $2.5 million a day — on consultants, broadcast ads and op-eds in Latino newspapers across the state.

"This looks like it's going to be the most expensive ballot measure ever," said David McCuan, a political science professor at Sonoma State University. "Not in California history, but in the history of the world."

The donor roster reads like a tech summit. Peter Thiel gave $3 million to the California Business Roundtable Super Pac in late December. Crypto mogul Chris Larsen has donated more than $23 million. Former Google CEO Eric Schmidt has given more than $42 million. Some donations arrived in cryptocurrency, incurring more than $40,000 in processing fees, filings show. DoorDash founder Tony Xu's company stock comprised another significant chunk.

The pro-40 camp, far less funded, has leaned on influencers and actors including Shepard Fairey and Mark Ruffalo. At a packed San Francisco rally this month, Vermont Senator Bernie Sanders said: "The whole country, and frankly people from around the world, are paying attention to what is happening here."

What happened in the redwood treehouse?

According to Bloomberg, Larsen hosted a Christmas party last December in a Marin County treehouse, with Janelle Monáe performing and Governor Gavin Newsom and Brin in attendance. Brin, worth about $245 billion, confronted Newsom and told him the tax was forcing him to leave California, people who spoke with Newsom told Bloomberg. Neither Newsom nor Brin responded to detailed questions.

By then, more than a dozen tech executives had joined an encrypted Signal group chat dedicated to burying the tax, the San Francisco Standard reported. Brin, Larsen, Marc Andreessen, Max Levchin, Patrick Collison and Ron Conway were members. The group met every Tuesday for months, debated fleeing the state, and tussled over trusting Newsom, who opposes state wealth taxes and says the measure would "drive a race to the bottom."

Most of the state's 200-plus billionaires have stayed. Nvidia CEO Jensen Huang said he's "perfectly fine" with the tax. Meta CEO Mark Zuckerberg threatened to leave but SEC filings last week show he struck a deal with his board to help pay the tax if Prop 40 passes in exchange for staying. Thiel, David Sacks, Larry Page and Brin have indicated departures; Brin bought a $42 million mansion on the Nevada side of Lake Tahoe in December.

How did the signature war play out?

Opponents tried to kneecap the union's signature gathering by flooding the ballot with rival measures, driving the going rate from $4 per signature to a record $36. Conway spelled out the goal on a March podcast: "Our job is to get Gavin to negotiate this so that it doesn't get to the ballot. So maybe they don't get the signatures."

When SEIU-UHW used mostly volunteers, opponents allegedly tried to buy the signature-collection firm outright. "That's what you would do in business: If there's an impediment, just buy it," one Signal chat participant reportedly wrote. Fred Kimball, president of Kimball Petition Management, said his company weathered denial-of-service cyberattacks and received two unsolicited calls about a sale. "My dad started this industry, there's no way I'd do that," he said. By late April the union had gathered 1.55 million signatures, nearly double the requirement.

The union offered to cut the tax from 5% to 2% if Newsom endorsed it. "Let's save patient lives together," the union wrote. "But that was a non-starter," Regan said.

What are the poison pills?

Two billionaire-backed countermeasures also made the ballot: Proposition 41, which directly targets the billionaire tax, and Proposition 42, which would ban wealth taxation outright. If either receives more yes votes than Prop 40, the tax dies even if it passes. Regan calls them "poison pills."

The opposition has landed endorsements from Planned Parenthood Affiliates of California, the California Teachers Association, the California Medical Association, plus gubernatorial candidate Xavier Becerra, former congresswoman Katie Porter and San Francisco mayor Daniel Lurie. Building a Better California spokesperson Abby Lunardini said the measure "would permanently gut the state's budget, tax base, and economic advantage, all while making the problem it's supposed to be fixing — healthcare funding — worse."

The Prop 40 campaign survived its Democratic defections. Congresswoman Maxine Waters pushed a reconsideration at an August party board meeting in San Diego, swinging the vote. The California Federation of Labor Unions AFL-CIO, with 1,300 affiliated unions, endorsed it overwhelmingly. "I'm not going to be a labor movement that bows down to the establishment and is scared of taking on billionaires," federation president Lorena Gonzalez said.

Where do the polls stand?

Six Nobel prize-winning economists endorsed Prop 40 last month, calculating that California billionaires' combined wealth of $2.3 trillion equals the annual income of all 20 million state taxpayers, and that their net worth has grown nearly 150% on the AI boom. "This tax only partially plays catch-up, but it is a move in the right direction," they wrote.

A Politico poll last week showed 84% of registered voters had seen Prop 40 ads, with most unpersuaded. The measure's lead has slipped from seven points over the summer to one. "This issue is going to be at the center of the nominating process for a Democratic candidate in 2028," Regan said.