傳統的研究智慧中，總統制和兩黨制的配套被認為是一個民主國家較容易運作的組合。主要的理由是兩黨制較不可能出現意識形態的極化，以及因為兩個政黨需要贏得中間位置的選票，其可以促成政黨之間較溫和及向心的競爭，因而有助於總統制的運作。然而，近年來，一些兩黨總統制國家發生嚴重的憲政危機，甚至促成民主衰退。為何這些兩黨總統制國家會走上民主衰退的道路，是本文所要探索的研究問題。首先，本文透過對於拉丁美洲兩黨總統制國家的個案分析發現，憲政結構的因素如總統和國會的權力抗衡會影響..

Past research argues that presidentialism and two-party systems are workable combinations that can facilitate democratic stability. The causal mechanisms are that ideological polarization is less possible to appear in a two-party system, that two parties needing to win votes from the center encourages moderation, and that the absence of the extremist parties and the centripetal nature of party competition favor democratic stability. However, in recent years, some presidential countries with a two-party system in Latin America..

法國與臺灣的政府體制都屬於半總統制，法國的憲政經驗中曾出現過三次的「左右共治」，臺灣的憲政經驗中卻從未出現過「藍綠共治」，何以如此?這是本文欲探討的課題。本文藉助賽局理論作為分析工具，探討制度安排如何影響行動者間的策略互動，以致最後產生了共治與否的差異。法國與臺灣擁有不同的選舉制度和不同的國會保障機制，在兩種制度因素的交互作用下，會引導分屬不同政黨陣營的總統和國會多數產生不同的政治計算與策略互動，最終導致法國出現「左右共治」，臺灣卻沒有出現「藍綠共治」。 ..

Both France and Taiwan’s political systems are semi-presidential. However, “cohabitation” in French constitutional experience has occurred three times while Taiwan has never seen “cohabitation” until now. Finding the reason for this difference is the central question of this paper. By using the game theory as an analysis tool, the paper explores how the institutional design influences the actors’ strategic interactions, which underlies the discrepancy between France and Taiwan in “coh..