Google co-founder Sergey Brin has poured another $20 million into Build a Better California, the organization leading the opposition to the state’s proposed billionaire tax, according to a new campaign filing. That brings Brin’s total contributions to more than $100 million — a sum that far exceeds the estimated $13.3 billion tax bill he would face under the measure.
Brin, whose net worth hovers around $267 billion, is the world’s fourth-richest person. His latest donation underscores the high-stakes battle over California’s Prop 40, which would impose a one-time 5% tax on the net worth of the state’s roughly 200 billionaires. The revenue would largely fund California’s healthcare programs, including Medicaid, which faces a potential $30 billion loss in federal funding once President Trump’s budget cuts take effect next year.
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Prop 40: What’s at stake
Prop 40, set for the November ballot, has become a flashpoint in the broader national debate over wealth inequality and tax policy. Proponents argue that the ultra-wealthy have benefited disproportionately from California’s economy and should contribute more to essential public services. Opponents, including Brin, contend that the tax would drive billionaires and their businesses out of the state, hurting the economy and reducing overall tax revenue.
Brin isn’t alone in his opposition. A wave of tech moguls have already left California in recent years. Meta founder Mark Zuckerberg reportedly purchased a $170 million mansion near Miami this year. Former Uber CEO Travis Kalanick, venture capitalist Peter Thiel, and Brin’s fellow Google co-founder Larry Page have also relocated. Their exits have fueled concerns about a “billionaire exodus” that could cost the state jobs and investment.
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Governor Gavin Newsom (D-CA) has voiced opposition to Prop 40, but for different reasons. Newsom worries the tax could accelerate the departure of wealthy individuals and their businesses. Instead, he has called for a “national billionaires’ tax.”
“Today, the office worker can shoulder a higher tax rate than the heiress,” Newsom wrote in a blog post. “We should end the ‘tax-free lifestyle loan,’ the gimmick that lets the ultra-wealthy borrow against their stock portfolios while reporting no taxable income.”
Brin’s strategy and counter-measures
Build a Better California, the organization Brin is funding, has proposed a set of opposing ballot measures that, if passed, could effectively block Prop 40 by making it harder to introduce new taxes in the future. This approach mirrors tactics used in other states where wealthy donors have used ballot initiatives to constrain tax policy.
Brin’s spending — more than $100 million — is unusual for a single donor on a state tax measure. It highlights how much the ultra-wealthy are willing to invest to protect their financial interests. The sum also dwarfs the estimated $13.3 billion Brin would owe under Prop 40, suggesting that his opposition is about more than just the immediate tax bill.
A rare voice of support: Jensen Huang
Not all billionaires are fighting the tax. Nvidia co-founder Jensen Huang, who would owe around $8 billion, has publicly embraced it. “I have not even thought about it once,” Huang said in a January interview with Bloomberg. “We chose to live in Silicon Valley, and whatever taxes they would like to apply, so be it. I’m perfectly fine with it.”
Huang’s stance stands in stark contrast to Brin’s aggressive opposition. It also highlights a philosophical divide among the tech elite over their obligations to the state and society.
What to watch next
Californians will vote on Prop 40 in November, and the outcome could have national implications. If the measure passes, it could embolden other states to pursue similar taxes on the wealthy. If it fails, it would mark a significant victory for billionaire donors and could discourage future attempts to tax extreme wealth.
The battle also raises questions about the influence of money in politics. Brin’s $100 million campaign is a stark reminder that the ultra-wealthy can shape public policy in ways that ordinary citizens cannot. As the November election approaches, both sides are likely to escalate their spending, making Prop 40 one of the most closely watched ballot measures in the country.
For now, the fate of the billionaire tax rests in the hands of California voters. But the fight over it has already revealed deep divisions over wealth, taxation, and the role of the state’s most successful residents in funding its public services.
