比較憲政工程多數的傳統智慧認為議會制是所有憲政體制中較佳的 類型，其主要的立論基礎是來自於英國兩黨制或是西歐多黨制國家成功運 作議會制的民主經驗。這些議會制國家之所以能夠成功的運作，需要一些 特定條件的配合，如具有實踐民主較久的歷史傳統以及良好的經濟成長支 持。然而，一些新興的民主國家並不必然具備這些助益的條件來鞏固議會 制的運作，甚至還可能出現民主運作失敗的經驗。如第二波民主化浪潮 (1943-1973)中，有十五個國家運作議會制失敗，甚至是出現民主瓦解的 結果。這十五個國家皆屬於兩黨議會制，其特徵是由取得國會多數的單一 政黨或是由一些政黨組成聯盟而執政。因為議會制立法和行政合一的特 徵，所以政府的組成和存續相對而言較為穩定。但是為何這些國家還是會 走上民主瓦解的道路？本文主要的目的在於探索為何這些新興國家在實 施民主的初期，運作議會制的經驗是失敗的。 本文主要發現如下：第一、當議會制國家面臨嚴重的社會和經濟危機 時，總理可能深陷黨内意見分歧的泥沼，無法有效因應外部的危機。第 二、議會制之下，執政黨黨内的權力結構是影響總理能否持續掌握政治權 力的關鍵。因此可能會出現獲得民意多數支持的總理，反而因黨内少數決 定性的反對意見而必須黯然下台，形成黨意凌駕民意的現象；第三、新興 民主國家的執政黨因為同時掌握行政和立法資源的分配，所以能夠在選舉 競爭中一直持續執政，甚至是形成優勢政黨體系（predominant-party system);相對地，反對黨無法成為強有力的政黨進而取代執政黨輪替執 政。亦即，議會制行政和立法合一的特徵，使得新興民主國家中控制權力 的執政黨握有重要的政治資源和分配，使其政治競爭的過程中保持相對的 優勢，進一步壓縮反對黨取得執政的空間和機會。第四、議會制和領先者 當選的選舉制度的配套（兩黨議會制）可能會惡化原本的社會族群分歧，促 成嚴重的族群衝突和暴力運動，甚至間接導致軍事政變。

Parliamentarism has become the paradigmatic type of constitution for most scholars, based on the successful experiences in U.K. and in some multi-party countries in West Europe. Some particular conditions such as long-term democratic experiences and high economic growth have fostered these advanced countries to successfully operate with parliamentary systems. However, some newly democratic countries did not have those factors to contribute to the operation of parliamentary system and even failed in some cases. The main purpose of this paper aims to explore how some particular political features contribute the failure of parliamentary system in some new democracies. Why some new democracies failed in operating parliamentary system, why some new parliamentary countries with a two-party system did not succeed like advanced parliamentary countries, what political features cause 全球政治許論 Review of Global Politics 第五十七期（2017) No.57頁25-60 that result are the research questions posed in this paper. By drawing the parliamentary countries suffering democratic breakdown in the second wave of democratization and the experiences in Malaysia and in Sri Lanka, this paper has four findings. First, when faced serious social and economic crises, the prime ministers in two countries were in a quagmire of division within the party and could not respond to those crises. Second, prime ministers with high popularity in parliamentary countries have to step down due to the rebellion against government by junior members of parliament (MPs). Third, because of the fusion of executive and legislative power in parliament system, the ruling party can be predominant in elections and form a predominant-party system or the opposition is too weak to compete with the ruling party. Fourth, the combination of parliamentarism and the first-past-the-post (FPTP) system has exacerbated the problem of social cleavage, even directly facilitating communal violence in a divided society. Overall, parliamentary system has some fragilities and drawbacks. Without some contributing factors, parliamentary systems might fail as well.