The Complexity of Strategic Behavior in Primary Elections
New study reveals why strategic voting in primaries is fundamentally unsolvable.
A groundbreaking computational social choice paper proves that strategic behavior in primary elections is extraordinarily complex. Researchers show determining if a pure Nash equilibrium exists is Σ₂ᴾ-complete, computing a best response is NP-complete, and finding subgame-perfect equilibria in sequential primaries is PSPACE-complete. These results, formalizing a model of primaries under first-past-the-post voting, reveal primaries fundamentally increase the computational difficulty of strategic reasoning far beyond direct voting systems.
Why It Matters
This mathematically validates why predicting primary outcomes is so difficult and has implications for designing more robust electoral systems.