Billionaire Backed Group Spends $276 Million Fighting California Wealth Tax

A political campaign financed by some of California's wealthiest technology executives and investors has raised $296.6 million to oppose a proposed billionaire wealth tax and promote two competing ballot measures ahead of the November 2026 election. Building a Better California has spent $276.6 million on its campaign, according to state campaign finance reports cited by the Mercury News on October 11.

The proposed Proposition 40 would impose a one-time 5% tax on the net worth of more than 200 California billionaires. Backed by SEIU United Healthcare Workers West, the measure would direct revenue toward health care, food assistance and education programs affected by federal funding cuts under President Donald Trump's legislation.

Google co-founder Sergey Brin leads the opposition group's donor list, contributing $102 million through October 3, according to campaign finance records. Other major contributors include venture capitalist John Doerr, with $40 million; former Google CEO Eric Schmidt, with $35 million; Stripe CEO Patrick Collison, with $33.1 million; and venture capitalist Vinod Khosla and Ripple Labs executive Chris Larsen, who each contributed approximately $12.5 million.

Political science professor Thad Kousser of the University of California, San Diego, said the potential financial consequences of the tax help explain the scale of the contributions.

"The stakes for these people personally are much, much higher than even these large donations," Kousser said.

Building a Better California has concentrated nearly 93% of its spending on Proposition 40 and the competing Propositions 41 and 42. The latter measures contain provisions that could prevent the wealth tax from taking effect if either receives more affirmative votes than Proposition 40.

According to the Mercury News, the group has directed $103 million to support Proposition 41, which would require state auditor reviews of proposed special taxes before they qualify for the ballot. Another $65 million has gone toward Proposition 42, which would prohibit new state personal property taxes. The group has spent an additional $88.5 million opposing Proposition 40.

Abby Lunardini, a spokesperson for Building a Better California, said the organization believes the state's economic future depends on responsible fiscal policy.

"future depends on maintaining our economic competitiveness and making smart, accountable public investments that will improve affordability and quality of life for all Californians." Lunardini said.

She also argued that Proposition 40 poses substantial economic risks.

"it will devastate the state's budget, tax base and economy," Lunardini said.

Explaining the group's support for the competing measures, Lunardini said it was "fighting for more transparency in government and stronger protections for people saving for retirement" through Propositions 41 and 42.

Republican political consultant and former California Chamber of Commerce official Marty Wilson said defeating the wealth tax remains the campaign's central objective.

"their first priority has to be the defeat of Proposition 40," Wilson said.

Wilson said the group could allocate less money to the other initiatives because they face little organized financial opposition.

"They've got two reform measures that don't really have any funded opposition, so they can lighten up their spending on those," Wilson said.

California's healthcare workers' union has raised nearly $31 million in support of Proposition 40 as of September 19, substantially less than the opposition campaign's fundraising total. A separate committee supporting Proposition 40 and opposing Propositions 41 and 42 has raised $340,000, according to the reported figures.

SEIU United Healthcare Workers West president Dave Regan acknowledged the financial imbalance between the campaigns.

"there's no question we can't compete in terms of financial resources," Regan said.

Regan said the union was instead seeking volunteers to counter what he described as an "avalanche of dishonest spending." Vermont independent Sen. Bernie Sanders also supported the tax campaign, appearing at rallies in Los Angeles and San Francisco.

Sanders described the proposal as the "most important ballot initiative in the country."

A September poll by the Public Policy Institute of California found that Propositions 40, 41 and 42 could all win narrow majorities. An October 10 editorial by the Press Democrat urged voters who support the wealth tax to reject Propositions 41 and 42, arguing that their provisions could block Proposition 40 despite receiving majority support.

The editorial also questioned provisions in Proposition 41 that would require audits before tax initiatives qualify for the ballot, potentially increasing state auditor costs. Proposition 42 would prohibit new state personal property taxes enacted after January 1, 2026, and restrict retroactive taxes.

California places no contribution limits on campaigns supporting or opposing ballot measures. The competing campaigns involving Propositions 40, 41 and 42 have spent more than $242 million during the current election cycle, according to the Mercury News.