半總統制已是全世界最多民主國家採用的憲法類型,其中大多數是新興民主國家。因為半總統制是一個憲政雙軌的憲政體制,對新興民主國家而言,民主化之後運作半總統制最常面臨的問題就是體制的運作是偏向總統制或是偏向議會內閣制。就實際經驗而言,這個問題容易受到政黨體系與制度設計共同影響,因此探究政黨體系與制度的特性,成為回答半總統制運作甚至轉型的關鍵變因。臺灣與蒙古是亞洲地區少數運作半總統制的新興民主國家,觀察兩國半總統制憲政體制的運作,臺灣已經大幅度偏向總統主導,而蒙古整體而言仍是憲政兩軌相互拉扯的結構。本文將從政黨體系的特性以及制度的比較,討論臺灣與蒙古在半總統制的體制中實際運作的經驗及其理論意涵。
Semi-presidentialism is now found in a plurality of the world’s democracies, especially among the new democracies. Semi-presidentialism is a constitutional bi-track system that shares commonalities with both pure presidentialism and parliamentarism systems of government. In many new democracies, the critical question faced by semi-presidentialism is: who is the de facto head of government? Is it the popularly elected fixed-term President, or the Prime Minister responsible to the legislature? The answer to this question is influenced by both institutional design and party system, two critical independent variables that affect constitutional operations. Taiwan and Mongolia are two newly semi-presidential democracies in Asia. However, the constitutional operation in Taiwan is closer to that found under presidentialism while Mongolia switches between presidentialism and parliamentarism. This paper discusses the theory and practice of semi-presidentialism in Taiwan and Mongolia.