This paper examines how presidentialism influences legislative party system formation by focusing on the Philippines. The country's posttransition party system is what Ekstein (1975) called a "crucial case": according to an acknowledged theory, the Philippine's set of conditions should have led to a two-party system, but multi-party system has continued since the 1986 democratization to present. In this concern the paper examines why the theory does not properly explain the current multi-partyism in Philippines. My analyses of the Philippine case demonstrate that the theory failed to give due attention to three issues: (1) the number of presidential candidates need to be taken as a variable, (2) presidential elections influence the organization of legislative parties by providing preferred party affiliation options for legislative aspirants, and (3) presidential elections affect cross-district variation rather than the number of parties competing at the district level. A comparative implication of this single-country study is that the influence of presidential elections on legislative party system formation may be found at the level of cross-district variation rather than at the level of the number of parties in each district.

論説