California Billionaires Spend $293 Million to Fight Proposition 40

California's proposed billionaire wealth tax has triggered a multimillion-dollar political battle ahead of the Nov. 3, 2026, election, with wealthy technology executives financing opposition to Proposition 40 while supporters argue the measure could protect healthcare services threatened by federal spending cuts. An analysis published by the Los Angeles Times on Oct. 23 found that billionaires and their spouses had contributed $293 million to oppose the proposal and support competing ballot measures designed to invalidate it.

Proposition 40 would impose a one-time 5% tax on the wealth of billionaires who resided in California on Jan. 1, 2026. The taxable amount would be calculated using their net worth on Dec. 31, 2026, with payments spread over five years. Estimates of the number of affected billionaires range from approximately 200 to 260, depending on the analysis.

According to the Los Angeles Times, just 30 billionaires or their spouses, representing about one in eight eligible billionaires, had spent money opposing the measure. Google co-founder Sergey Brin contributed $102 million, more than one-third of the total billionaire opposition funding identified by the newspaper.

An economic analysis by Jasper Boll, Emmanuel Saez and Gabriel Zucman, published through the National Bureau of Economic Research in August, estimated that the measure could generate at least $107 billion after accounting for some tax avoidance and evasion. The four wealthiest Californians identified in the Times analysis—Brin, Jensen Huang, Larry Page and Mark Zuckerberg—would collectively owe approximately 40% of the estimated tax revenue.

Supporters say the money would primarily fund state healthcare programs, with additional allocations for food assistance and education. At a rally at the University of California, Berkeley, Rep. Ro Khanna argued that the proposal would help preserve coverage for millions of residents affected by federal funding reductions.

“It works because it raises the billions of dollars that will be needed so 3.5 million Californians don’t lose health care,” Khanna said.

The campaign has also drawn opposition from Gov. Gavin Newsom and political groups aligned with wealthy donors. According to NBC Bay Area, organizations opposing Proposition 40 had spent a combined $88.7 million on advertising through the election, based on figures from ad-tracking firm AdImpact. Some spending also supports Propositions 41 and 42, which would nullify Proposition 40 if either receives more votes.

Political correspondent Guy Marzorati of KQED described the competing campaigns as a central question in the election debate.

“You see ads not only opposing Prop 40 but also for Prop 41 and Prop 42, those two measures on the ballot to nullify proposition 40,” Marzorati said.

Saikat Chakrabarti, a supporter of Proposition 40, criticized Newsom's opposition, alleging that the governor was concerned about maintaining relationships with wealthy donors. Newsom's office did not respond to NBC Bay Area's request for comment.

Opponents argue that taxing billionaires could encourage them to relocate, reducing California's future income-tax collections and potentially affecting businesses and jobs. Dave Johnson, chairman of the Silicon Valley GOP, said entrepreneurs could move their companies and employees to other states if the measure passed.

“If you kill the engine which in other words those billionaires are typically entrepreneurs of they have established companies if you tax them even a one-time tax they could just move to another state and take their employees with them,” Johnson said.

Estimates of the measure's financial impact vary substantially. Researchers associated with Stanford University's Hoover Institution have projected lower revenue, with estimates ranging from approximately $30 billion to $40 billion after accounting for potential relocations and legal challenges. Supporters maintain that the tax could raise roughly $100 billion, while the California Legislative Analyst's Office has described the potential proceeds as tens of billions of dollars.

Alan Auerbach, an economics professor at the University of California, Berkeley, has cautioned that taxpayer mobility makes the projections uncertain. He said the potential revenue could be offset by future income-tax losses if wealthy residents leave the state.

California's billionaire population has experienced substantial wealth growth in recent years, according to the Los Angeles Times' analysis of Forbes data. Much of that wealth is held in company shares, and unrealized gains generally are not taxed as income until assets are sold. The newspaper reported that Brin and Page disclosed no taxable income in three of the years since 2019.

Meta announced a new class of nonvoting shares on Wednesday, Oct. 21, intended to allow Zuckerberg to sell stock to cover a potential tax bill while retaining his voting power. The arrangement was tied to his commitment to remain in California for eight years, according to the Los Angeles Times.

Chris Hoene, executive director of the nonpartisan California Budget and Policy Center, disputed the assumption that purchasing property elsewhere necessarily establishes a change of residence. The state's Franchise Tax Board would ultimately determine residency and calculate the taxable wealth, excluding real estate, pensions and retirement accounts.

“The reality is the income tax loss can never get anywhere near the scale of what the wealth tax gain would be,” Hoene said.

Polling ahead of the Nov. 3 election has shown a tightening contest. A September survey by the University of California, Berkeley's Institute of Governmental Studies found that 45% of likely voters supported Proposition 40, compared with 42% opposed, while 13% remained undecided. An earlier March poll recorded 52% support and 33% opposition, indicating that the measure's initial advantage had narrowed.