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U.S. Senator Bernie Sanders has criticized Google co-founder Sergey Brin over the money he has committed to opposing California’s proposed billionaire wealth tax. Brin has contributed more than $100 million to Building a Better California, a group fighting Proposition 40 and supporting competing tax measures.
The political fight has also attracted attention on crypto-based prediction market Polymarket. Polymarket traders currently assign about a 28% probability to a California billionaire wealth tax meeting the market’s resolution criteria in the November 3 election, with roughly $3.7 million traded.
Sanders Criticizes Brin’s Opposition Spending
Sanders argued that Brin could afford the proposed tax even if he were liable for billions of dollars. Using his own estimate of Brin’s wealth and potential liability, he said:
“If California passes its one-time 5% wealth tax, he would owe $14 billion and still be worth $270 billion.”
Brin recently added another $20 million to Building a Better California, taking his contributions to the group above $100 million. The organization has raised more than $110 million as wealthy technology and investment figures campaign against Proposition 40.
Proposition 40 Would Impose One-Time 5% Tax
Proposition 40 would impose a one-time tax equal to 5% of net worth on billionaires who were California residents on January 1, 2026. Real estate, pensions and retirement accounts would generally be excluded, while affected taxpayers could spread payments over five years subject to an additional charge.
The official voter guide says 90% of the revenue would go toward healthcare, with the remainder allocated to education, food assistance and administration. California’s Legislative Analyst estimates the measure could generate tens of billions of dollars over several years, while also potentially reducing annual income-tax revenue if some billionaires leave the state.
Polymarket Traders Favor Proposition 40 Rejection
Polymarket’s 28% implied probability means traders currently favor the measure failing, although prediction-market prices can change before the election. Governor Gavin Newsom also opposes the proposal, while Sanders and the California Democratic Party support it.
The outcome is further complicated by Propositions 41 and 42. California’s official voter guide says either measure could prevent Proposition 40 from becoming law if it receives more votes and courts determine the measures conflict.
