Coalition Formation Analysis

Coalition formation analysis is the formal study of which subset of parties will combine to form a governing or decision-making coalition when no single party commands a majority. William Riker's 1962 The Theory of Political Coalitions supplied the foundational logic: under pure office-seeking, rational politicians form minimal winning coalitions and, by the size principle, the smallest winning coalition possible, so that the spoils of office are divided among as few partners as necessary. Michael Laver and Norman Schofield's 1990 Multiparty Government enriched this with policy-seeking motives, showing that coalitions also tend to be ideologically connected. The framework predicts coalition membership from seat shares and party positions.