The Japanese party system changed from the previous one-party dominance with the reform of the electoral system in the House of Representatives in 1994. After the political realignment, the LDP/Komeito and the DPJ constituted the two-party system in 2003. However, in 2012, the DPJ split while remaining the ruling party, and after the return of the LDP to power, non-LDP parties split off, creating a system that overlaps with the one-party dominance system of the past.
This paper examines the hypothesis that the competition among parties within the system itself may lead to the vulnerability of the system, because explanations of the change of the Japanese party system that focuses on voter-level changes and electoral reforms do not capture the changes that have occurred since 2012.
