California’s Proposition 40 wealth-tax battle has attracted more than $100 million from Google cofounder Sergey Brin and additional funding from venture capitalist John Doerr and crypto billionaire Chris Larsen, while strategist Ned Wigglesworth helps lead the opposition campaign. The measure would impose a one-time 5% levy on roughly 200 Californians who had at least $1 billion in wealth as of Jan. 1, potentially raising about $100 billion, primarily for health care after federal Medicaid cuts. Opponents have reserved $87 million in advertising and warn that wealthy residents could leave or alter their investments, reducing revenue from existing taxes; former White House economic adviser Tomas Philipson said those losses could exceed the new tax receipts. The debate has also revived scrutiny of Wigglesworth, who once criticized wealthy donors for using political spending to protect their interests. Gov. Gavin Newsom opposes the state measure while supporting higher federal taxes on the ultrawealthy, and business leaders remain divided over its effects on California’s tax base and startup investment.