Risk, institutions, and policy in decisions to join a start-up party: Evidence from the 2017 snap election in Japan

Research has shown that Japan’s parallel electoral system altered the incentives that parties and their members face when competing for lower-house seats, leading to, among other things, more policy-oriented and less personalistic elections. What is less well known is how these altered incentives affect the decisions of incumbents to stay with their current party organizations or exit and join another political party. We address this question by using data from the 2017 snap election in Japan, specifically, the exit decisions of Democratic Party of Japan (DPJ) incumbents. Typically exit decisions involve considerations of electoral support, policy, or increased office benefits. Our results indicate that policy considerations were a primary factor in DPJ members’ exit decisions but also that exiting legislators considered the risks associated with these decisions, which was molded by available party alternatives, each’s electoral strength, and a unique feature of Japan’s electoral rules, the fact that it reduced the electoral risk for some but not all incumbents who contemplated switching parties.