在戰後日本民主憲政史上，2005 年舉辦的第 44 屆日本眾院議員選舉深受各界重視，特別是因為該屆選舉，是日本政治史上首度因重大政策遭國會否決，內閣首相逕予交付民意定奪的一項公民複決選舉。當時自民黨的執政內閣能否在改選中贏取民心，亦或由民主黨等在野黨派來更迭政權，不僅攸關小泉純一郎首相政治生命與改革路線的延續，更牽動日本未來政經局勢的發展走向，其重要性確實不容小覷。

有別於過往研究囿限於宏觀層次或質化的研究途徑，本文嘗試根據日本選舉研究(JES)在 2005 年彙整的民意調查資料，希望以個體資料估算出自民黨執政聯盟的選戰策略，對選民在 2005 年眾院改選時的投票影響力;當中特別是郵政改革議題、小泉個人魅力及刺客戰術的效果，更是本文關注的焦點。研究結果發現，除了選民政黨認同、保革意識型態等持續吻合既有日本選舉文獻的討論外，更重要的是，自民黨針對這次選戰的競選策略也相當成功，除郵政民營化的改革議題在大選中深受選民肯定，小泉個人領導魅力也為執政聯盟帶來正面的選票效果。本文透過多層模型分析的結果，雖適度地驗證許多文獻的推論，但我們也發現刺客戰術並未如一般預期給自民黨帶來實質的加分。統計的結果發現，自民黨造反派議員仍舊在選區中擁有一定的實力，只是這些反叛議員所獲得的支持會被選民對郵政改革的偏好所沖淡。

The 44th Japanese House election in 2005 has played a significant role in its post-war democratic history and also drove a lot of attention in the academics. The importance of this election, regarded as the national referendum for the postal reform, relies on the fact that it is the first time the House is dismissed because of unsolved policy gridlock. The consequence of the election not only results in the destine of LDP coalition government and the political career of Prime Minister Junichiro Koizumi, but also the development of Japanese politics and economy.

Apart from previous literatures limited to macro and qualitative perspectives, we use the Japanese Election Study (JES) survey data to measure the voting behavior of this campaign. Of all the factors that might influence the voters, we are especially interested in the postal reform, LDP nomination strategy, and Koizumi’s charisma. The result first shows the significance of party identification and political ideology in influencing the voting behavior, which is consistent with the existing researches. More importantly, the election strategies adopted by Junichiro Koizumi and his party indeed work out well. We find people’s standpoint on the privatization of postal system, and their attitude toward Koizumi as well, which led to the support for the ruling coalition candidates. Although our multilevel analysis confirms many inferences of previous literatures, LDP “assassin” nomination strategy cannot be counted as one of them. We find those rebel congressmen still dominate in their electoral districts. Although the support is diluted by voter’s enthusiasm for the postal reform.