Google co-founder Sergey Brin has contributed $102 million in 2026 to Building a Better California, a political group supporting two California ballot measures that could prevent a proposed tax on billionaires from taking effect, according to state disclosure data reported by the Los Angeles Times. His latest disclosed contribution was $20 million.
The spending places Brin at the center of an increasingly expensive contest over three measures headed to California voters in November. Proposition 40 would impose a one-time 5% tax on the assets of people worth at least $1 billion who lived in California on January 1. Its supporters say 90% of the proceeds would go to healthcare, with the remainder directed to education and food assistance. They estimate it could raise about $100 billion, although the state's Legislative Analyst's Office has said the exact total is difficult to predict and would probably amount to tens of billions.
Building a Better California is supporting Propositions 41 and 42. Proposition 41 would establish audit requirements for new state special taxes and restrict taxes whose proceeds are excluded from a state spending limit. Proposition 42 would bar new taxes on retirement holdings, individually owned assets and other personal savings, while also prohibiting retroactive taxes on previous earnings.
The Legislative Analyst's Office concluded that either competing measure could block the billionaire tax if it wins more approval votes than Proposition 40. Supporters of the wealth tax therefore view the measures as direct obstacles, while their advocates present them as protections for taxpayers, savings and government accountability. Building a Better California describes itself as a nonpartisan organization concerned with affordability, quality of life, innovation and economic growth. The group declined to discuss Brin's contributions with the Times.
The wealth-tax coalition includes SEIU-United Healthcare Workers West, the California Democratic Party and Senator Bernie Sanders. Opposition also extends beyond technology executives: the California Chamber of Commerce, Governor Gavin Newsom, the California Teachers Association and Planned Parenthood Affiliates of California are among the prominent opponents identified by the Times. Critics argue the proposal could encourage very wealthy residents to leave and weaken the state's economy.
Other technology and venture-capital figures have contributed to the opposition effort, including Chris Larsen, Ron Conway, John Doerr, Michael Moritz and Stripe chief executive Patrick Collison. Brin's unusually large contribution nevertheless defines the financial scale of the campaign. The final outcome will depend not only on whether voters support taxing billionaire wealth, but also on how they resolve the competing provisions across all three propositions.
