The Power Relationship between the Prime Minister and Ruling Party Legislators: The Postal Service Privatization Act of 2005 in Japan

This article examines the power relationship between the prime minister and ruling party legislators. I theoretically explore the power relationship between the prime minister and ruling party legislators, and examine legislators' parliamentary voting, focusing on the political process of postal service privatization of 2005. This analysis presents three arguments. First, theoretically, when the prime minister attempts to achieve a project, risking his or her job, he or she can firmly control ruling party legislators. Second, empirically, the anti-Koizumi legislators' rebellion was based on their unfounded assumption about the prime minister's behavior or ultimate outcomes. Third, the anti-Koizumi legislators' electoral incentives to secure their reelection and ruling incentives to weaken or overthrow the Koizumi Cabinet drove them to rebel against the prime minister in the Lower House, while the ruling incentives alone caused the rebellion in the Upper House.