Billionaire opponents of California's proposed wealth tax have spent more fighting the measure than they have on any prior political cause in the state, according to a Politico analysis of campaign records published Wednesday¹.

Politico found a record $612 million from more than 70 current and former California billionaires flooding this year's state elections, with more than $293 million from at least 30 of them going to groups working to defeat Proposition 40 on Tuesday's ballot¹.

The initiative would impose a one-time 5 percent tax on assets of billionaires who lived in California as of Jan. 1, 2026¹. Proponents say it is needed to backfill federal health care cuts¹.

Google co-founder Sergey Brin is by far the opposition's biggest benefactor, Politico reported, with former Google CEO Eric Schmidt, venture capitalist John Doerr, Stripe CEO Patrick Collison and crypto executive Chris Larsen among the largest contributors¹.

Much of the money has flowed through Building a Better California, a new Brin-led political operation¹. Politico said Doerr has given $40 million and Ripple's Chris Larsen $17.5 million¹. Current CEOs including those of DoorDash, Roblox, Robinhood, Stripe, Affirm, Figma and Rippling have collectively put at least $88 million into the cause¹.

Frank Slootman, Snowflake's board chair and former CEO, who gave $5 million and had no prior California campaign record, told Politico the measure upends basic assumptions about being a taxpayer and a resident of a state¹.

Building a Better California spokesperson Abby Lunardini said in a statement that supporters of the group share a commitment to policies that protect the state's economic, jobs and innovation engine¹. The group argues the measure would damage the state tax base and budget while undermining the health care funding it is intended to patch¹.

Debru Carthan, vice president of SEIU-United Healthcare Workers West, the union behind the tax, said, "no amount of billionaire spending is going to intimidate us or turn us back"¹.

Politico said the other half of billionaire spending this year came largely from Tom Steyer, a rare billionaire endorser of Prop 40 who funded his own failed gubernatorial bid¹. The previous high-water mark in Politico's tally was 2010, when billionaires spent $147 million on state races and measures, much of it Meg Whitman's self-funded run for governor¹.

Gov. Gavin Newsom has publicly opposed a state-level billionaire tax, Politico reported¹. Several opponents say they have left California or, in Brin's case, registered to vote in Nevada; Anduril founder Palmer Luckey said he plans to stay and keep fighting the measure¹.

The New York Times also published a story on billionaires fighting Prop 40; its full text was not available for this filing².