不同的制度往往彼此鑲嵌，難以切割觀察。對於此問題，相關文獻常以「加總法」來探究制度配套的課題。本論文認為，採用此法可能會忽略制度配套對原有制度性質的改變。以中央政府體制和政黨體系的搭配為例，多黨制在內閣制之下可能縮短政府的壽命，但在總統制之下卻能助長行政部門的優勢。本論文根據既有制度論的研究發現，推演出幾項關於制度配套和政治效能的命題，指出兩黨制可能因內閣制或總統制而產生迥異的後果，而行政部門與立法部門的選舉時程，對於總統主導下的府會關係則有關鍵的影響。對於經歷2005年修憲的台灣而言，正可運用這些命題來探討未來憲政運作的可能後果。由於此次修憲案設下了極高的修憲複決門檻，在可見的未來台灣將以半總統制和傾向單一選區制的選舉制度為主軸。此種搭配可能因為一致政府而享有高效能，也可能因為分立政府而導致嚴重的朝野對抗。行政與立法的改選時程，因而成為影響未來政局的關鍵因素。

Institutionsare usually embedded in each other and can hardly be analyzed independently. Existing studies, by aggregating the effect of individual institutions to assess their overall influence, could underestimate the impact at the systematic level when the institutions are considered together. Multipartism, for instance, may shorten government duration under the parliamentary system, but enhance the administrative power if presidentialism is used. Inline with existing institutional studies, this paper derives several propositions regarding the impact of institutional configuration on political stability. Bipartism can result to diverse outcomes when it is used under parliamentarism or presidentialism, and electoral cycle plays a crucial role in determining political stability when a president is in charge. These propos-itions are then applied to forecast Taiwan's constitutional future. The latest constitutional revision set up a high threshold for further amendment to be reconsidered by the people, making semi-presidentialism and a single-member-district biased electoral system the defming features of Taiwan's constitutional structure. Since this combination could lead to the greatest and the lowest stability, electoral cycle will be critically influencing Taiwan's constitutional prospect.