**Proposition 40**, the one-time 5% wealth tax on roughly 200 California billionaires resident as of January 1, 2026, faces strong structural headwinds on the November 3 ballot. Two competing measures—Propositions 41 and 42, backed by over $205 million in opposition spending led by Sergey Brin—would nullify the tax even if Prop 40 secures a majority by banning new taxes on personal property, financial assets, or those circumventing state spending limits. Governor Gavin Newsom endorsed Prop 42 in early October, aligning with business and tech opposition. September polling showed Prop 40 support between 45% and 52%, while experts highlight implementation complexity, expected litigation, and prior billionaire relocations that have already reduced the potential tax base. These factors drive trader consensus that the measure is unlikely to take effect.