Sergey Brin has now put more than $100 million into defeating a California ballot measure that could cost him $13 billion — a ratio that explains why the fight is worth it to him, and why it is being waged with money rather than argument.

A filing Friday shows Brin donated another $20 million to Building a Better California, a political advocacy organization opposing the state’s billionaire tax, bringing his total contributions to $102 million. Brin, the world’s fourth-richest person with a net worth around $267 billion, faces an estimated $13.3 billion payment if the measure passes.

Under Proposition 40, billionaires who were California residents on Jan. 1, 2026 would owe a one-time tax equal to 5% of their net worth, due in 2027, with the option to spread payment over five years at additional cost. It would hit roughly 200 people, with 90% of the revenue directed to the state’s healthcare program and 10% to education, food assistance and administration. Backers, led by the labor group SEIU-UHW, project it could raise as much as $100 billion.

The fiscal hole behind the measure is real. California’s Medicaid program alone could lose up to $30 billion in federal funding once the Trump administration’s budget cuts take effect next year.

The opposition strategy is not simply to defeat Prop 40 at the ballot. Build a Better California is separately backing two competing measures, Propositions 41 and 42, described by supporters as attempts to keep Prop 40 from ever taking effect by restricting the state’s ability to introduce new taxes at all. One of the qualifying measures would require audits of programs funded by new state special taxes. All three go before voters in November.

The other defense is already underway, and it is the one that matters most for California’s tax base. Brin now lists Nevada as his residence in state records and reportedly bought a $51 million home near Miami Beach in March. Larry Page has converted several assets out of California, incorporating his family office Koop in Delaware in December 2025, with the nonprofit Oceankind similarly reincorporated around the same time. Travis Kalanick, Peter Thiel and Page have all left the state, and Mark Zuckerberg reportedly bought a $170 million mansion near Miami this year.

That mobility is the structural problem with a state-level wealth tax, and it is why the measure has split the Democratic side rather than uniting it. Governor Gavin Newsom opposes Prop 40, citing the economic impact of billionaires and their businesses leaving California, and has called instead for a national billionaires’ tax. Writing that an office worker can shoulder a higher tax rate than an heiress, Newsom argued for ending what he called the tax-free lifestyle loan — borrowing against stock portfolios while reporting no taxable income. A federal version removes the exit option that a state version cannot.

There is not yet clear evidence establishing how much of the relocation activity is attributable to Prop 40 specifically. Residency changes among the very wealthy have been running for years, driven by state income tax rates as much as by any single ballot measure.

Spending above $100 million from a single donor on a state tax measure is unusual, and the sum is dwarfed by the $13.3 billion at stake — which suggests the campaign is aimed at more than one election. The approach mirrors tactics used in other states where wealthy donors have funded ballot initiatives to constrain future tax policy.

California has become the center of the debate over the K-shaped economy and the diverging fortunes it produces. November decides whether the state tests the theory that wealth can be taxed where it is held rather than where it is earned.

JBizNews Desk | San Francisco

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