In California, the First Billionaire Tax Meets Its Most Expensive Opposition

There is a quiet arithmetic to wealth in California—a state where the top one percent of households pay nearly half of all personal income taxes, where fortunes are built in the valleys of Silicon Valley and the hills of Palo Alto, and where a single ballot measure has now drawn a line in the sand between two visions of what prosperity owes to the common good . Proposition 40, the first-in-the-nation wealth tax on billionaires, has become a mirror held up to a state that is both extraordinarily wealthy and extraordinarily unequal.

The measure, which will appear on California’s ballot this November, would impose a one-time five percent tax on the assets of roughly two hundred residents and trusts with a net worth exceeding one billion dollars as of January 1, 2026 . The revenue—estimated at up to one hundred billion dollars—would flow into a Billionaire Tax Reserve Fund, with ninety percent earmarked for healthcare and the remainder directed toward education and food assistance . For its supporters, including the Service Employees International Union-United Healthcare Workers West, Senator Bernie Sanders, and Representative Ro Khanna, the tax represents a long-overdue reckoning with a system that has allowed the wealthiest to accumulate staggering fortunes while paying a smaller share of their income in taxes than their secretaries .

Yet the opposition has been swift, well-funded, and deeply personal. Google co-founder Sergey Brin, whose estimated tax liability under the measure would exceed thirteen billion dollars, has donated more than one hundred million dollars to defeat the initiative . In December 2025, as the proposition was being drafted, Brin purchased a mansion near Lake Tahoe and listed Nevada as his home state—a move that critics described as a flight from responsibility and supporters dismissed as an exaggeration of the tax’s reach . The broader opposition campaign, organized under the banner Building a Better California, has raised approximately three hundred eighteen million dollars from a roster of billionaire donors including venture capitalist John Doerr, former Google CEO Eric Schmidt, and Ripple co-founder Chris Larsen .

The fight has split California’s Democratic establishment in ways that mirror the national party’s broader tensions. Governor Gavin Newsom, who has long opposed state-level wealth taxes out of concern that the wealthy will leave and take their income tax revenue with them, has endorsed Proposition 42—a competing measure funded by Brin that would not only cancel Proposition 40 but ban all future taxes on personal property, including pensions, 401(k) accounts, and investment holdings . “We all agree that Californians deserve to have their retirement and life savings protected from new state taxes,” Newsom said in a statement released by the measure’s proponents . The union backing Proposition 40 responded sharply: “By voting yes on Prop 42, he’s showing California his true colors. He’d rather millions of children and families lose their healthcare than ask a couple hundred billionaires to finally pay their fair share” .

The economic arguments on both sides rest on contested ground. Six Nobel Prize-winning economists, including Joseph Stiglitz, Paul Krugman, and Daron Acemoglu, signed a letter arguing that the tax is “modest compared with billionaires’ wealth gains” and that California has attracted eighty percent of all new venture capital funding since the start of 2026, up from roughly fifty percent before . Opponents point to a Manhattan Institute poll showing only thirty-five percent support for Proposition 40, compared to fifty percent opposed . They warn that the measure is a “Trojan horse” that could eventually reach middle-class assets, and they cite the exodus of billionaires like Brin as evidence that capital will flee before the tax can be collected .

What remains unanswered is the question that has shadowed every debate about wealth and obligation since the first gilded age: whether a society can ask its most fortunate members to contribute more without losing them entirely, and whether the fear of their departure is itself a form of power that no ballot measure can overcome.

The images accompanying this article are AI-generated for illustrative purposes only.

Sources: Deseret News, CalMatters, Fortune, The Hill, Cato Institute, Bloomberg TV Bulgaria