選舉制度影響政黨體系，是廣為人知的因果推論。依此邏輯，若以政黨體系為因，以選舉制度的變化為果，即產生內生性的選制變遷理論。然而，某些研究者仍認為選制變革起於和政黨體系無關的外生因素。本文主張，選制變遷是否受到政黨體系的影響，取決於選制的種類。第一，有利大黨的多數決選制如果始終未出現一黨過半，則國會屬於多黨制，有可能因為小黨組成多數聯盟而改採比例性選制。尤其當現狀為並立式單一選區兩票制時，可能因為小黨的議席多來自政黨名單，而比代表區域主義的多數決選制更容易導致..

It is well known that electoral system shapes party system. By this logic, an endogenous explanation for changes in electoral systems should treat party system as the cause and changes as the consequence, in sharp contrast with theories attributing changes to exogenous factors that are irrelevant to party system. This paper argues that whether changes in electoral system are caused by party system depend on the type of the electoral system. First, if a majority party never emerges from a majoritarian electoral system, minor p..