Proposition 42, a November 2026 California constitutional amendment, would bar new state taxes on personal property ownership such as retirement accounts, investments, and business interests while limiting certain retroactive levies tied to pre-enactment residency or conduct. The closely contested odds around 50% reflect a balance between support from high-net-worth donors seeking to constrain wealth taxation and opposition from Governor Gavin Newsom along with labor groups favoring revenue measures like the competing Proposition 40 billionaire tax. Key factors include overlapping ballot language where the higher-vote measure could nullify aspects of the other, plus ongoing legal debates over retroactive residency rules and due process. Polling trends, campaign spending patterns, and turnout among swing voters in key regions could shift probabilities ahead of election day.