Inverse Relationship between Party and Party System Institutionalization: The Transformation of Postwar Japanese Party Politics

The aims of this article are to clarify the relationship between institutionalization of political parties and institutionalization of the party system as a whole, and to explore the mechanisms of change in this relationship at a micro level. This article identifies four patterns in institutionalization and de-institutionalization of parties and the party system. It is theoretically conceivable not only that institutionalization and de-institutionalization may proceed concurrently, but also that, as a party system is institutionalized, political parties themselves may become de-institutionalized; or, conversely, that de-institutionalization of the system is accompanied by institutionalization of parties. A review of postwar Japanese party politics reveals that as the one-party dominant system became institutionalized, the dominant party was de-institutionalized from the inside by factionalism and clientelism among members. The one-party dominant system was replaced by a more competitive party system from the 1990s onwards, the factionalism that formerly held sway within the dominant party was suppressed, and the dominant party became united by conservative ideology. Nevertheless, the institutionalization and de-institutionalization of parties and the party system are macro-level concepts, and lack the capacity to account for micro-level mechanisms of change. This article is therefore based on the hypothesis that the pattern and degree of competition among political parties exerted influence on the power of the dominant factional coalitions and factions within Japan’s Liberal Democratic Party (LDP), leading to change in the party’s organization and policies. We will test the hypothesis by analyzing data gathered from members of the House of Representatives.