An Optimization Case Study in Analyzing Missouri Redistricting.

This article analyzes the impact of Missouri's new constitutional redistricting criteria and political geography on state legislative and congressional district plans using a local search optimization framework incorporating the recombination (ReCom) method. The study constructs district plans that satisfy Missouri's legal requirements—including population balance, contiguity, compactness, preservation of political subdivisions (counties), and Voting Rights Act compliance—and evaluates them with multiple fairness metrics such as compactness, efficiency gap, shifted efficiency gap, partisan asymmetry, and competitiveness. Results indicate that Missouri's political geography and constitutional mandates, particularly the preservation of political subdivisions and a shifted efficiency gap threshold, substantially limit improvements to political fairness in state legislative plans, often producing an inherent Republican advantage due to Democratic voter concentration in urban centers. In contrast, congressional plans, which are subject to fewer constraints, can be optimized to achieve significantly better political fairness scores while maintaining compactness and majority-minority districts. The study highlights trade-offs among fairness metrics and suggests that transparent computational analyses can inform stakeholders and support advocacy for fair and legally compliant redistricting.