California voters face competing ballot measures in the November 2026 election, with Proposition 42 positioned as a direct counter to a proposed one-time wealth tax on billionaires. The measure would amend the state constitution to bar new taxes on personal property ownership, including financial assets and retirement accounts, and restrict retroactive taxes applying to pre-enactment conduct or residency status. Qualification followed signature verification in June 2026, after negotiations involving Governor Newsom and legislative leaders failed to remove the billionaire tax initiative. Heavy spending by business interests backing the prohibition and labor unions supporting the wealth tax has kept the contest tight, with trader consensus reflecting uncertainty over turnout among key voter blocs, legal vulnerabilities of retroactive provisions, and trade-offs between revenue goals and taxpayer protections. Upcoming campaign developments and any late polling shifts could alter the balance before election day.