Abstract
Various variables have been considered to explain prime-ministerial power: constitutional and legal power resources, the power of the bureaucracy, electoral system, and power resources of the party leadership. This article alternatively emphasises the significance of the governing party as the key variable to explain prime-ministerial power. This article employs the principal-agent model; it pays particular attention to the governing party as principal of the prime minister. The problem for the governing party as principal derives from the fact that it is composed of multiple actors. It could be referred to as the ‘multiple principal problem’. Its fundamental nature is a collective action problem. Therefore, if the governing party can overcome its collective action problem, it can control the prime minister, while if otherwise, it will have extreme difficulty in doing so. By focusing on the collective action problem, this article explains the changing structure of the Liberal Democratic Party and its impact on the power of the prime minister in Japan.
