Missouri voters will decide Proposition A, a veto referendum on the Republican-controlled legislature’s 2025 mid-decade congressional map (HB 1), on November 3, 2026. The Missouri Supreme Court unanimously ruled on September 3 that the citizen-initiated referendum is valid under the state constitution, ordering it onto the ballot and barring use of the new lines until voters approve them, which reinstated the 2022 map for the general election. The secretary of state certified the measure on September 8 after earlier rejection attempts, though the state attorney general has appealed to the U.S. Supreme Court amid parallel federal litigation creating conflicting orders on which map applies in November. The new boundaries were drawn to favor Republicans and were challenged by a petition drive that collected over 300,000 signatures. Traders assign a modest edge to rejection, reflecting the referendum’s role as a direct voter check on partisan redistricting and the organized opposition to the mid-decade change.