民主政治不可缺少政黨，因此政黨的領導人在政治體系的運作中亦扮演不容忽視的角色。在特定的憲政體制條件和政黨政治生態下，一個政黨黨主席的產生，除了具有黨內領導權競爭性質外，也可能同時兼有角逐政府領導權的意涵。本文從政黨組織與憲政制度之理論，提出兩個政黨發展的軸線：「政黨選舉機器化」以及「政黨總統化」，以民進黨爲例，勾勒其從公元1986年創黨以迄2015年的政黨（組織）性格的變遷，以及伴隨著的黨主席角色與選舉競爭型態。研究發現，民進黨從創黨至今，爲在各次選舉中贏得勝選，原有使命型政黨的性格減弱，整個大方向較傾向政黨選舉機器化的發展。然而，這並不意味民進黨只是單向的發展進程，長期來看仍同時並存使命型與選舉機器兩種性格，並相互拉鋸。再者，在總統優勢的半總統制下，競逐總統大位的因素與其政治機會結構，牽動著黨內菁英爭取黨主席的計算和決擇，民進黨從而也走向政黨總統化的路徑。最後，在「政黨選舉機器化」以及「政黨總統化」的交織牽引下，黨主席的競爭，常成爲黨內總統候選人選舉的前哨戰，黨主席一職也被賦予更多和總統職位的連結意涵，甚至就是總統本人來擔任。

It is impossible to have a modern democracy without political parties. Leaders of political parties therefore play a vital role in the operation of a political system. The l competition over party chairmanship, in addition to the struggle for a leadership role within that political party, is sometimes also related to the competition over the leadership in ruling the government. This paper aims to explore the role of DPP’s chairman and the patterns of the competition over the party’s chairmanship from 1986 to 2015 by studying from two analytical dimensions on party organizations: the degree of being a presidentialized party and that of being an election-machine. The results have shown that from the founding date until now, the DPP’s original characteristic as a missionary party has gradually reduced, and the main direction of party development is shifting towards the end of being an election-machine. However, in the long run, the DPP is a mixture of both missionary intent and an election-machine. Furthermore, under Taiwan’s semi-presidentialism structure, the DPP is more like a presidentialized party. Consequently, the president of the country tends to serve as the chairman of the ruling party as well and the competition for the party chairmanship among the party elites also tends to resemble the competition for the presidency of the country.