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..

由於先天即存在應然與實然的落差，加上後天多元研究取向所導致立論之分歧，使得半總統制常有評價之爭議。因此，論者在研究中除了應正確認識半總統制的理論內涵，亦需謹慎進行案例的比較或應用，始能產生更精確、細緻的研究成果。本文出於這樣的關懷，將從理論層面出發，透過相關文獻檢閱與不同研究方法之回顧，重新發現半總統制的分析焦點及不同運作類型之內涵及變遷方向。再者，本文也將進行半總統制案例的初步檢驗，以確認半總統制國家實際運作的不同樣態與其中原因。 ..

Since Maurice Duverger proposed the concept of semi-presidentialism in 1980, disputes have increasingly been raised among researchers. Given the gap between norms and operations of semi-presidentialism, as well as the complexities among the relationships of president, prime minister, and congress in the operations of semi-presidential countries, this paper develops a theory-driven comparative framework of this concept. Through re- examining the definitions of semi-presidentialism and the methodology of analyzing its operation..