Sergey Brin has donated another $20 million to Building a Better California, taking his total backing for the anti-Proposition 40 group to $102 million as California voters prepare to decide in November on a one-time 5% wealth tax on qualifying billionaires. U.S. Sen. Bernie Sanders escalated the fight on X, saying Brin has made $140 billion since President Donald Trump was elected and would owe $14 billion under the measure while still being worth $270 billion, yet is spending $100 million to stop it. Forbes currently lists Brin's net worth at $260 billion, while the Bloomberg Billionaires Index had previously pegged it at $284 billion at the start of the week. The campaign now spans competing ballot measures, healthcare funding and warnings about capital flight. Supporters say Proposition 40 could raise roughly $100 billion, with 90% of the proceeds earmarked for healthcare and 10% for education and food assistance, although the Legislative Analyst's Office said the total is hard to predict and would probably be in the tens of billions of dollars. Building a Better California is also financing Propositions 41 and 42, which the Legislative Analyst's Office said could nullify Proposition 40 if they win more votes. Brin has likened the proposal to the socialism his family fled in the Soviet Union, and California Gov. Gavin Newsom opposes the state tax on the grounds that it could drive wealthy residents away even as he backs a federal minimum tax on Americans with more than $100 million in assets.