Missouri voters face Proposition A on November 3, 2026, a veto referendum on House Bill 1, the Republican-backed 2025 congressional map that would redraw districts to target a 7-1 GOP advantage by splitting Kansas City across multiple districts. A successful "yes" vote would uphold the new lines for future cycles, while "no" would preserve the 2022 map already in use for the 2026 election following Missouri Supreme Court rulings. Grassroots opponents collected over 300,000 signatures to qualify the measure, secured unanimous court validation of the referendum process, and launched substantial advertising against approval. Republican efforts to support the map have mobilized later in the cycle amid the legal timeline. These factors underpin the market's 74.5% probability on rejection.