Re-election Incentives and Defection: Party Switching in the Japanese Liberal Democratic Party

This article examines the switches of the LDP members of parliament from an historical perspective and focuses on explanations for this behavior. Unlike conventional studies of party switching predict that the new mixed electoral system will enable party leaders to rein in their legislators, I find that switches occur more frequently in the new system. To solve this puzzle, I investigate the party-legislator relationship and assert that legislators switch party when staying in the party jeopardizes their reelection. The threats to their reelection not only come from public dissatisfaction with government performance, but also from the lashing of party discipline. Based on this argument, I claim that in the SNTV era, the LDP MPs defected because of avoiding punishment from the discontented electorate. In the mixed system, they switched party affiliation due to the conflict between constituency interest and party policy.