本文主要探討在半總統制下，影響民主崩潰的制度與非制度因 素，並提出影響民主崩潰的可能機制。結合委任代理人、否決者與政 變論點，本研究認爲總統議會制相較於總理總統制易產生組閣爭議與 政策僵局，提高了政變介入與行政獨裁的機會，易於發生民主崩潰。 透過存活分析結果顯示因爲總統議會制有著制度設計上的缺失，其民 主崩潰的風險高於總理總統制。經濟因素中，僅GDP成長率對民主崩 潰有負向且顯著的影響。先前成功政變經驗愈多，由於可降低軍方官 員從事政變的風險並形成政變的牢籠，故提高民主崩潰的機率。變項 間交互作用分析結果顯示總統議會制結合不佳的經濟發展或是先前成 功政變經驗並不會顯著提高民主崩潰的可能性。

This study aims to explore both the institutional and non-institutional factors under semi-presidentialism that may lead to the collapse of democracy, and to study the mechanisms of these democratic crises. Utilizing the principal-agent theory, veto player theory and coup theory, this research argues that compared with premier-presidentialism, president-parliamentary constitutions are more probable to create disputes regarding the formation of the government as well as policy paralysis between the assembly and the elected president, thereby increasing the likelihood of coup intervention and administrative dictatorship, both being detrimental to democratic survival. The results of survival analysis are as follows. Firstly, owing to the institutional drawbacks of president-parliamentarism, its chance to experience a democratic breakdown is higher than the other subtype of semi-presidentialism. Secondly, of all the economic factors, GDP growth rate is the only significant variable and has a negative impact on the dependent variable. Thirdly, countries that had historically experienced more successful coups will have a higher likelihood to suffer from democratic collapse, due to lower risk faced by their military officials engaged in the coup and the coup trap. Finally, our results also show that president-parliamentarism, combined with poor economic development and possible coup threats, does not necessarily generate a high possibility of ending in a democratic collapse.