本文主要是補充論述自民黨為何在2009年的眾議院選舉中再度失去政權。2009年8月的眾議院選舉結果,自民黨大敗,民主黨取代自民黨執政,「自民黨為何再度失去政權?」成為日本政治過程研究的焦點。既有的研究主要集中在二個面向:一為論述2009年政權輪替的意義;二為利用「出口調查」的統計資料,分析選民的投票行為,特別針對中間選民與自民黨支持者的投票行為,造成政權輪替的現象提出具有說服力的論述。然而,既有的研究對於自民黨「為何」失去中間選民與自民黨支持者支持的原因,並未提出充分的說明;再者,本文研究發現,自公兩黨選舉合作的鬆動也是造成自民黨再度失去政權的重要因素。
The main purpose of this article is to further discuss why Japan's LDP had lost political power once again. The current analysis on LDP's failure of the 2009 Election is centered on two perspectives: one is to look for implications of party transition in t he government due to the result of the 2009 Election; the other is to employ data of exit poll focus on electorate voting behavior, in order to show that party transition in the government is a result of decreased vote from median voters and LDP supporters. However, the existing studies lack explanation to the main reasons of why the LDP was unable to maintain continual endorsement from median voters and LDP supporters. Further, this article argues that the collapse of LDP-Komeito electoral alliance is one other critical cause for the LDP to lose political power once again.