This theoretical work presents a systematic re-examination of the evolution of party politics in Japan since the end of World War Two. Due to the long one-party dominance by the Liberal Democratic Party, Japan's parliamentary democracy has often been viewed as unique in the developed world, with such determinants as its political culture, historical background and socio-ideological cleavages being considered. According to the author, these explanations do not adequately account for some of the most important changes that took place in Japanese party politics during the post war period. This study advances an alternative set of interpretations based on a micro-analytic approach that highlights the incentive and bargaining power of individual political actors and their competitive and strategic behaviour under existing institutional constraints. According to Kohno, the evolution of political life in postwar Japan depends on the same factors that are acknowledged to be at work in other industrialized nations.He reveals, through case studies of government formation processes and statistical examinations of candidate nomination patterns, that the microanalytic approach can establish fo