【研究目的】
本文藉由整合理性選擇制度論（rational choice institutionalism）中「否決者」（veto players）與歷史制度論（historical institutionalism）中「否決點」（veto points）的概念，透過對「行動者與決策影響時機」的闡釋與分析，討論「制度否決者」（institutional veto players）在政策產出過程中的互動，及這種互動與政策產出的影響。為了討論這樣的關聯性，本文選擇台灣全民健保政策的三個經驗案例，作為驗證理論的關鍵個案，並從這個驗證的過程中同時回答前述公共政策研究傳統的核心：「誰掌控政策產出」問題。

【研究方法】
本文以理論發展為始，從否決者與否決點的角度，建構一個觀察經驗世界的理論基礎。從這個基礎上，本文以立意選擇的方式，找出三個全民健保政策的關鍵事件，作深入的分析，分別是「全民健保法規劃及審議」的過程、「軍人納保」事件、以及「健保雙漲」事件等，從其中以大個案當中三個小個案的分析方式，討論前述的理論問題，最後據此作出結論。

【研究結論】
本文的結論有三：一、本文理論上整合否決者與否決點的觀點，希望能提供一個政治可行性的評估架構，然由於制度環境的不同，應用於台灣的經驗研究仍只具有部份的解釋力；二、雖然否決者的觀點在預測決策的產出結果是有力的分析工具，然在經驗上，卻必須面對定位否決者間意識型態相對位置的問題；三、在三個健保個案中，最具否決權的否決者仍是以國會為主，顯見即使在專業性高的政策場域，仍有政治介入的空間，平衡官僚的自主性。

Scholars in public administration often study the policy-making process through three major approaches: formal institutional procedure, interest group politics and rational decision-making model. However, none of these approaches can help us to grasp the constant changes of “power map”. Beginning in the 1990s, a series of comparative studies on “veto players” and “veto points” seem to shed the light to supplement the gap. According to the new approach, the crucial veto players and their ideologies on policy spaces could be identified to depict and classify the power maps under different veto points. This study attempts to follow this idea to study the changing relations of forces between three major veto players: executive leaders (elected and appointed politicians), congress, and bureaucracy in Taiwan’s National Health Insurance policy. Three cases are to be studied to test the political feasibility in the empirical study and three research outcomes will be demonstrated as well. First, in spite of the fact that it can offer a unified approach to predict the policy outcome, it still has the difficulty in identifying the veto players’ idea points and relative locations on the policy space. Second, for those who are searching for “localized power map” to analyze political feasibility in Taiwan, this study is a primary but useful beginning. Lastly, with regard to the most powerful veto player of Taiwan’s National Health Insurance policy from 19862004, there is no doubt that the congress shows critical influence in the policy making process.