California voters face competing November 2026 ballot measures on state taxation, with Proposition 42 seeking to bar new taxes on personal property ownership such as retirement accounts and financial assets while restricting retroactive tax liability based on prior residency or conduct. This measure directly conflicts with Proposition 40, a union-backed one-time wealth tax on billionaires that applies retroactively to January 1, 2026 residency. The slim 52.5% implied probability for passage reflects balanced trader assessments of campaign spending by business-backed supporters versus union opponents, limited early polling data, and uncertainty over which proposition secures more votes if both pass. Upcoming factors that could shift odds include fall advertising volume, endorsements from state leaders, and any shifts in voter views on protecting savings versus raising targeted revenue.