Missouri voters face Proposition A on November 3, 2026, a veto referendum on House Bill 1, the congressional map enacted in a 2025 special session and signed by Governor Mike Kehoe. The measure would replace the 2022 districts with new boundaries intended to deliver a 7-1 Republican advantage by shifting the Kansas City-based 5th district. A citizen petition drive by People Not Politicians gathered more than 300,000 signatures in December 2025, suspending the law. After the Missouri Supreme Court unanimously upheld the referendum’s constitutionality in September 2026 and the U.S. Supreme Court declined further stays, the 2022 map remains in use for the current election cycle. Traders assign 75% probability to rejection, reflecting the scale of the opposition campaign and the referendum’s role as a direct check on mid-decade legislative redistricting.