Billionaires Fighting California’s Wealth Tax Have Put $333 Million Into Political Ad Machine Ahead of Elections

California's top earners have mobilized and poured more than $300 million into an aggressive public campaign to defeat the controversial Billionaire Tax Act at next week's midterm elections.

The measure, which will appear on the Nov. 3 ballot as Proposition 40, would impose a one-time tax of up to 5% on the global assets of roughly 200 Californians with a net worth of $1 billion or more who resided in the state as of Jan. 1, 2026. 

Championed by a coalition of labor unions, the proposed tax is intended to help fund healthcare for low-income households affected by the the Trump administration's Medicaid cuts. But in the process, it has ignited fierce, bipartisan opposition among California's richest 1%.

To eliminate what they view as an existential threat to their business interests, dozens of Silicon Valley billionaires banded together this year to launch Building a Better California, a political action committee. The exceptionally well-funded nonprofit's stated goals include defeating Proposition 40 and, at the same time, supporting two countermeasures.

State campaign finance filings reviewed by the New York Times show that roughly 80 deep-pocketed donors, led by Google/Alphabet co-founder Sergey Brin, former Google CEO Eric Schmidt, and prominent investor John Doerr, have spent more than $333 million on the PAC.

Brin alone provided $102 million during the first six months of the PAC's existence, before turning off the money spigot and encouraging others to open their wallets.

Silicon Valley builds a war chest

The tech mogul, whose personal net worth is currently estimated at over $240 billion, according to Forbes, has long been a vocal critic of the billionaire tax.

Since the proposal was first introduced, Brin has shifted several Alphabet entities and assets from California to Florida and purchased property in two states: a $51 million Miami megamansion on Florida's Allison Island and a $42 million mansion on the Nevada side of Lake Tahoe.

Former Google CEO Eric Schmidt donated $40 million to the campaign to defeat Proposition 40. (Craig Barritt/Getty Images for TIME ; Realtor.com)

Following in Brin's footsteps, Schmidt and Doerr each contributed $40 million to the cause, followed by Patrick Collison, CEO of Stripe, an online payment processing company, who chipped in $33 million.  

According to the Times reporting, existing donors to the campaign have been recruiting fellow business leaders to join the fight by contributing cash or stock and becoming actively involved in the PAC. 

Top venture capitalists, as well as tech entrepreneurs from companies such as DoorDash and Robinhood, have reportedly answered the call. 

Bipartisan backlash

Opposition to the tax extends beyond the tech industry. Outgoing Democratic Gov. Gavin Newsom, who had tried and failed to keep the proposal off the ballot, has warned that it would lead to an outflow of capital from California, erode the state’s tax base, and stifle innovation with little to show for itself. 

California Gov. Gavin Newsom fiercely opposes the proposed billionaire tax and previously tried to defeat it. (Michael Kappeler/picture alliance via Getty Images)

A large share of the PAC's war chest has funded statewide advertising to urge California voters to reject Proposition 40 and approve the two rival initiatives. 

Proposition 41 would require audits of new state special taxes, while Proposition 42 would ban new taxes on personal property, including financial portfolios and retirement savings. 

If both Propositions 40 and 42 pass but the latter captures more votes, it would invalidate the billionaire tax.

Beyond traditional TV ads, the campaign has been bombarding voters with anti-Proposition 40 messaging through streaming services, video games such as SimCity, and old-school paper mailers.   

According to internal documents reviewed by the Times, Building a Better California is committed to delivering a decisive blow to Proposition 40 on Tuesday to "chill wealth-tax efforts nationally."

Spending chasm

Records reviewed by the Los Angeles Times show that the anti-Proposition 40 camp is outspending its opponents supporting the measure nearly 10 to 1.

Proponents of the tax on California's wealthiest residents have raised $34.3 million, primarily from the Service Employees International Union-United Healthcare Workers West, which sponsored the ballot measure. 

However, most of those funds were spent on collecting signatures to qualify the tax proposal for the ballot, leaving the pro-measure camp with just $1.6 million in its coffers as of Oct. 17, according to the L.A. Times. 

Operating on a shoestring budget, campaigners have been sending voters emails and text messages urging them to embrace Proposition 40 while rejecting Propositions 41 and 42 backed by the Silicon Valley elites. 

Speaking to the L.A. Times, Suzanne Jimenez, chief of staff of the healthcare union, downplayed the colossal funding gap.  

"The billionaires think voters are stupid," she told the outlet. "Their spending also makes our case for us. When billionaires can afford to spend millions a day protecting their fortunes, voters can see that billionaires have plenty of money to spare."