Newsom Backs Measure to Block California's Billionaire Tax, Siding With Brin-Funded Campaign

California Governor Gavin Newsom announced on Friday, October 9, 2026, that he is endorsing Proposition 42, a ballot measure funded and placed on the ballot by Google co-founder Sergey Brin that would cancel a separate proposal to tax billionaires' wealth and bar any similar tax in the future, according to CalMatters and KPBS.

The announcement came roughly three weeks before California voters decide on three competing tax measures in the November 3 general election: Proposition 40, which would impose the one-time wealth tax, and Propositions 41 and 42, both designed to stop it from taking effect.

What the three measures do

Proposition 40, titled the One-Time Wealth Tax for State-Funded Health Care Programs Initiative on the official ballot, would impose a one-time 5% tax on the net worth of California residents with assets exceeding $1 billion as of January 1, 2026, according to the California Secretary of State's voter guide. Backers, led by SEIU-United Healthcare Workers West, say 90% of the revenue would go to the state's Medi-Cal health program, with the remainder for food assistance and education, according to CalMatters. The official argument in favor of the measure, filed with the Secretary of State, says it would apply to roughly 200 billionaires and could raise about $100 billion for those programs.

Proposition 41 would require audits of special-tax ballot measures and could invalidate Proposition 40's tax if it does not comply with existing state spending limits, according to CalMatters and KPBS.

Proposition 42 would cancel Proposition 40 outright and prohibit any future tax on personal property, including retirement accounts such as pensions and 401(k)s, investments, business holdings and art collections, according to CalMatters and KPBS.

Newsom's position and reaction

Newsom opposes Proposition 40 and, according to CalMatters and KPBS, has not yet taken a public position on Proposition 41. In backing Proposition 42, he said Californians' retirement and life savings should be protected from new state taxes, a position reported by KPBS and CalMatters.

The endorsement drew criticism from within his own party. Debru Carthan, a vice president at SEIU-United Healthcare Workers West — the union that placed Proposition 40 on the ballot — said Newsom would "rather millions of children and families lose their healthcare than ask a couple hundred billionaires to finally pay their fair share," according to CalMatters and KPBS. The California Democratic Party has endorsed Proposition 40, and Democratic Representative Ro Khanna has accused Newsom of prioritizing donor relations over policy, per KPBS.

Money behind the campaign

Opposition spending has dwarfed support for the wealth tax. Building a Better California, the main committee formed to defeat Proposition 40 and pass Propositions 41 and 42, had raised about $317.5 million as of mid-October, according to the political-finance tracking site Inside Political Money. Supporters of Proposition 40 had raised roughly $32.2 million, funded almost entirely by SEIU-United Healthcare Workers West, the same source reported.

Google co-founder Sergey Brin funded and placed Proposition 42 on the ballot, according to CalMatters and KPBS; the sources reviewed for this article did not specify a dollar figure for his personal contribution. Police and fire unions have also backed Proposition 42, according to KPBS.

Arguments on both sides

In the official voter guide, the argument in favor of Proposition 40 — signed by representatives of SEIU-United Healthcare Workers West, Planned Parenthood of Pacific Southwest and American Federation of Teachers Local 1521 — says billionaires pay lower effective tax rates than working families and should help restore health coverage lost to federal policy changes.

The argument against, signed by representatives of the California Medical Association, the California Primary Care Association and the California School Boards Association, cites a Stanford University study estimating the tax could cost the state $25 billion as companies and wealthy residents relocate out of state, and warns it lacks accountability safeguards and could eventually affect ordinary retirement accounts.

What is still unknown

As of this reporting, Newsom has not stated a position on Proposition 41. The exact legal mechanism for resolving the ballot if voters approve both Proposition 40 and one of the countermeasures was not detailed in the sources reviewed for this article. Independent, non-partisan polling on how California voters intend to vote on the three measures was not available in the sources reviewed either.