California's tech billionaires have assembled a $340 million war chest to defeat Proposition 40, a one-time 5% wealth tax on the state's billionaires. The opposition campaign is spending more than $1 million per day — $21.2 million in the first 19 days of September alone — on robotexts, mailers, and streaming ads. Google co-founder Sergey Brin alone has contributed $102 million. Former Google CEO Eric Schmidt has put in $42 million. The yes campaign, funded primarily by the SEIU-UHW healthcare union, has raised just $33 million total. The donor list reads like a Silicon Valley org chart: Peter Thiel, Tony Xu, Patrick Collison, Chris Larsen, and a bench of venture capitalists. Their money flows primarily through a Super PAC called Building a Better California, which has funneled more than $297.8 million since July into the three campaigns opposing the tax. None of the opposition messaging mentions billionaires. Instead, ads feature a doctor in a white lab coat warning the tax is "a harmful tax scheme" and testimonials from teachers, carpenters, and firefighters. The opposition's most sophisticated move isn't the ad spend — it's the ballot architecture. Opponents placed two counter-measures, Propositions 41 and 42, on the same November ballot. Prop 41 directly targets the billionaire tax; Prop 42 broadly shields individuals from certain new taxes. If either receives more yes votes than Prop 40, the billionaire tax dies even if it passes. Political scientist David McCuan calls them "poison pills" designed to exploit voter confusion: "When voters are confused, when they are uncertain, it's much easier to get a no vote." The coalition assembled against Prop 40 is deliberately ecumenical. Governor Gavin Newsom opposes it. Both the Democratic and Republican candidates for governor — Xavier Becerra and Steve Hilton — oppose it. Katie Porter, the progressive former congresswoman known for grilling corporate executives, has become a face of the opposition, writing op-eds and appearing in ads. Planned Parenthood Affiliates of California is listed as a paid contractor in campaign filings. The campaigns have donated tens of thousands to county Democratic parties, though those parties have endorsed Prop 40 anyway. The consultants hired tell their own story. Nielsen Merksamer, a Republican-leaning law firm known for defending tobacco companies, handles legal strategy. PCI Campaigns, which fought propositions to repeal the death penalty and require condom use in pornography, runs political operations. The opposition has explicitly targeted Latino voters with Spanish-language ads and articles framing the tax as "una buena idea, mal construida." Polling shows the strategy is working. A late-September UC poll found 45% yes to 42% no — a 3-point margin, down from a 7-point lead a month earlier. The narrowing tracks directly with the spending ramp. If passed, Prop 40 would impose a one-time 5% tax on California's billionaires, with proceeds funding healthcare programs for 3.4 million Californians, along with some education and food assistance. The SEIU-UHW says the measure is necessary because of federal healthcare funding cuts under Trump's One Big Beautiful Bill Act. Bernie Sanders traveled to California last week to rally for the measure, calling it "the most important ballot initiative in the country." Proponents and opponents agree on one thing: Prop 40 is a test case. If a wealth tax passes in the state with the most billionaires, the template travels. That's exactly why the opposition is willing to spend $340 million to stop a one-time tax — the precedent is worth far more than the levy itself.
