政黨勢力的消長、演變與政治分歧焦點的轉變，向來都被證實具有密不可分的互動相隨關係。根據西方選舉政治的經驗，衍生出來兩種解釋的理論取向：一為強調社會結構分工所導致利益衝突的社會分歧論；另一為經濟社會條件改變與社會化過程所形成世代差異的價值變遷論。台灣近年來政黨的演變，雖屬於競爭性政黨萌芽時期的一種特徵，然而新生的政黨為了生存發展，必然也會回溯到既存在的社會分歧上，找尋歷史文化的支點，以動員支持群眾。此外，也因為台灣社會處於台海兩岸分裂國家的對立、競爭與可能合作的歷史情境。因此，政黨競爭與選舉政治所凸顯出來的政治分歧，在性質上則截然不同於西方民主社會的情形。 本文應用兩筆全國性的面訪調查資料，以互為補充與驗證的方式，一方面說明與檢視台灣政黨演變與政治分歧的特殊性，另方面也剖析與解釋民進黨、國民黨與親民黨之選民基礎何在。本文將心理上認同與行為上投票支持同一政黨的忠貞選民、以及沒有政黨認同但也投票支持該政黨的未來認同者，皆視為該黨的選民基礎而稱之為「民基」。 本文的分析發現：三黨的民基在省籍、族群認同、國家認同、統獨議題立場、台灣前途決定權認知、台灣心、中國情與李登輝情結等變項上，皆具有統計上的顯著差異。這些影響變項所指涉的，也就是當前台灣社會的政治分歧所在。這些政治分歧焦點，可以追溯到長久以來潛藏於文化價值與深植人心的、所謂「中國結」與「台灣結」之因素。以比較總體的角度來觀察，台灣社會的政黨演變與選舉競爭的訴求，基本上可說是被定位在這兩個既融合且分裂的交叉座標上打轉或移動。以2000年總統選舉資料所顯示的，台灣政黨的分合與選舉競爭的性質，可說是屬於文化價值的一種認同性衝突，截然不同於歐美社會選舉政治顯現的政策立場之功能性衝突。最後，本文也從政黨民基的相對位置與政治分歧，來說明民進黨、國民黨與親民黨等三黨在總統選舉所顯現的勢力消長。

Party change and the shifting of loci of political cleavages have well been found going hand in hand. Upon electoral politics in Western societies, two theoretical explanations are often cited to explain their relationship. One is related to social cleavages, as Lipset and Rokkan suggest in their seminal article. The other is attributed to Inglehart’s value change theory. However, in Taiwan as it’s burgeoning of competitive party systems has experienced, each newly-formed party may have eventually gone back to old cleavage structures to ground its grass roots. And, since the complicated relationship between the Taiwan Strait unsettled yet, the party competition and political cleavages are to be inevitably tied up with the “Taiwan vs. China” tension, thus, fundamentally different to those counterparts in Western democracies. With an analysis of two survey data sets in a mutually complementary way, in the one hand I tried to outline the nature of party change and political cleavages in Taiwan, and to identify and locate the electoral bases of the DPP, KMT and PFP on the other. A party’s electoral base (min-chi) is operationally defined as those supporting voters who identified the party as well as those non-partisan voters who did voted for the party. As evidenced in data analysis, voter’s ethnicity, ethnic group identification, national identity, unification-independence issue stance, attitudes toward who have the right to decide the Taiwan’s future, Concerns for Taiwanese society or whole Chinese society, and Lee Teng-hui complex are all significant factors distinguishing the partisan divisions among DPP, KMT and PFP. It is argued that political cleavages in Taiwan are basically derived from the deep-seated cultural traditions, namely, so-called “Taiwanese complex” and “Chinese complex” at the macro-level. Consequentially, the party change and electoral competition in Taiwan have been confined to relate these two factors. As testified with the 2000 post-electoral survey data, party change and electoral competition in Taiwan are related more to identification issues than to policy options, which have long been intrinsic to electoral politics in the Western democracies. Finally, a tentative answer to why the DPP won, KMT lose, and PFP consolidated in this presidential election was spelled out in terms of the shift and swing of electoral bases along with the entwined axes drawn by identification issues.