California's Proposition 40 — a one-time 5% tax on individuals with net worth exceeding $1bn — went down in the most expensive ballot fight in state history. The opposition, funded almost entirely by the people who would have paid the tax, spent nearly $425m to defeat it. Sergey Brin alone contributed at least $132m. At peak intensity in early October, anti-Prop 40 spending exceeded $2.5m per day. The measure was sponsored by SEIU-United Healthcare Workers West and backed by major unions, Bernie Sanders, and Ro Khanna. Proceeds would have funded healthcare programs, with some directed to education and food assistance. Supporters framed it as a backstop against healthcare cuts flowing from Trump's One Big Beautiful Bill Act. The opposition framed it as "an everyone tax" — a messaging gambit that proved decisive despite the tax applying exclusively to billionaires. The opposition's tactical sophistication went beyond advertising. Billionaire donors bankrolled two counter-measures — Propositions 41 and 42 — designed as structural kill switches. Prop 41 directly targeted the billionaire tax; Prop 42 proposed a blanket ban on any future wealth taxation. Either measure needed only to receive more yes votes than Prop 40 to nullify it, even if Prop 40 itself passed. Supporters accurately called them "poison pills," but accuracy doesn't win ballot fights. Governor Gavin Newsom opposed Prop 40, as did both the Democratic and Republican candidates for governor and, notably, Planned Parenthood Affiliates of California. Their objections centered on the measure's structure as a one-off tax funding only specific healthcare programs — a legitimate policy critique that also provided bipartisan cover for the opposition campaign. The donor list read like a Silicon Valley directory: executives from Google, Palantir, DoorDash, Stripe, and Reddit, plus a roster of prominent venture capitalists. The ratio tells the story. Billionaires spent roughly $425m to avoid paying a one-time tax that would have raised — by design — a comparable sum. The expenditure was not irrational: it purchased a precedent. Any future state-level wealth tax proposal now faces the demonstrated willingness of the ultra-wealthy to spend dollar-for-dollar to kill it, plus the Prop 42 template for embedding permanent bans into law. The national implications are immediate. Wealth-tax proposals in other states — and the broader "billionaires should pay their fair share" movement — just lost their most viable proof-of-concept. California was the best-case scenario: a deep-blue state with a large billionaire population, a sympathetic healthcare framing, and union organizational capacity. If the tax couldn't pass here, proponents will struggle to argue it can pass anywhere. What persists is the structural asymmetry. The people subject to the tax had the resources to defeat it and did so by a margin that signals the fight was never close on the dimension that matters most in ballot campaigns: money. The democratic process functioned as designed — voters chose — but the information environment those voters inhabited was shaped by a spending disparity that no union or progressive coalition can match.
