Sergey Brin is building a political organization that will last beyond his $102 million fight against Prop 40
Google co-founder Sergey Brin has spent much of his career on the fringes of electoral politics.
But a proposed wealth tax in California has made the billionaire one of the state’s most powerful political financiers, inspiring him to create an organization that can continue to shape state policy long after voters have decided on the measure that initially mobilized him.
Brin contributed $102 million to Building a Better California, a political organization that has become the primary vehicle for Silicon Valley billionaires seeking to influence California’s political direction. The group has raised hundreds of millions of dollars from wealthy tech executives, venture capitalists and business leaders, funneling the money into ballot measures that go beyond the immediate fight against Proposition 40.
Two measures written to kill the tax
Through October 20, Building a Better California has spent more than $304 million to support efforts to defeat Proposition 40 and advance Propositions 41 and 42, direct counterattacks to the wealth tax. Of that amount, about $118.5 million was spent opposing Proposition 40, while the remaining $186 million supported Propositions 41 and 42, according to Capital and main.
Proposition 41 would prohibit the state from exempting new taxes from its spending cap and require state audits of programs funded by new special taxes, making it harder for the state to use funds raised through the billionaires tax. Proposition 42 would ban retroactive taxation, directly countering Proposition 40. The strategy gives ultra-wealthy opponents multiple opportunities to defeat the measure: If either gets more “yes” votes than Proposition 40, according to the Legislative Analyst’s Office, the wealth tax could be stopped even if a majority of voters approve it.
And according to an analysis of PolicyMore than 70 current and former California billionaires have contributed a record $612 million to national elections in the 2026 cycle. Nearly half of that money has gone to groups working to defeat Proposition 40 and at least 30 billionaires have contributed more than $293 million specifically to fighting the wealth tax, according to the analysis.
Building a Better California also endorsed Propositions 1, 3, 37, 41 and 42, according to its policy platform. He also invested $10 million in Proposition 45, a separate measure addressing California’s environmental assessment process, and $6 million in Proposition 37, which would create a $25 billion homeownership loan fund, according to Capital and main.
The electoral measure that awakened the billionaire beast
The immediate catalyst for the ultra-rich movement was Proposition 40, a proposed one-time tax on the wealth of California billionaires that will appear on the November 3 ballot.
The measure would impose a 5% tax on the assets of individuals and certain trusts worth more than $1 billion who resided in California as of Jan. 1, 2026. The proposal aims to raise money to offset reductions in federal health care funding, with 90% of revenue allocated to health care and the remaining 10% directed to education and food assistance. The state would likely collect tens of billions of dollars from the tax, spread over several years, according to the Legislative Analyst’s Office.
The proposal was sponsored by the Service Employees International Union-United Healthcare Workers West, which argued that California needs additional funds to protect its health care system as federal cuts threaten residents’ coverage. The ballot measure is also supported by progressive leaders Sen. Bernie Sanders (I-Vt.) and Rep. Ro Khanna (D-Calif.).
For Brin, whose fortune is estimated at $231 billion by Bloomberg, the potential financial risk is considerable – and he has been particularly vocal about his opposition. In an interview with The New York Times in April, he compared the proposal to the socialism he experienced growing up in the Soviet Union, saying he didn’t want California to end up in the same place. He also moved to Nevada in December, ahead of the Jan. 1 deadline that determines which billionaires would be subject to the proposed tax.
But rather than leave the California political fight behind him, Brin mounted a coordinated campaign to prevent the measure from becoming law.
Sergey Brin did not immediately respond to a request for comment from Fortune.
In January, Brin created Building a Better California, making an initial contribution of $20 million. As of August, his contributions had reached $102 million, according to campaign finance filings.
The organization has since become a major coordination point for wealthy tech executives. Other major contributors include John Doerr, chairman of Kleiner Perkins, Eric Schmidt, former CEO of Google, Patrick Collison, CEO of Stripe, and Michael Moritz, former partner at Sequoia Capital.
Even Mark Cuban, a self-described “libertarian at heart” and billionaire with close ties to Democrats in recent years — for example as a high-profile surrogate for Kamala Harris in the 2024 presidential race — has found himself siding with his wealthy compatriots. Cuban engaged in a public feud with Khanna on X over the proposal, ultimately calling the politician “crazy”.
“This is the biggest f*** in the history of entrepreneurship,” Cuban wrote on X. “Never.”
Some billionaires just want the wealth tax dead
But not everyone shares Brin’s overall policy goal. His political organization has faced resistance from at least one major donor over the extent of expanding its political agenda. Former Google CEO Eric Schmidt was one of the ultra-wealthy sponsors who had problems with Brin’s broader focus on politics.
The New York Post initially reported in August that Schmidt had become frustrated with the anti-wealth tax coalition led by Brin after the group failed to stop California Democrats from approving the measure.
But a close adviser to Schmidt said Fortune in August, the former Google CEO was not “angry” about the outcome of the endorsement and that Schmidt’s “only current involvement in politics is his contribution to defeating the billionaires tax” — meaning Schmidt and Brin differed on the group’s money going toward other measures, such as Proposition 45.
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