This study uses a natural experiment offered by the Hungarian National Assembly, where the mandate type (single member district vs. party list or proportional representation (PR)) changes for a number of legislators each term, to explore whether and how change in mandate type causes change in legislators’ voting behavior. We perform (1) a simple difference-of-means test, (2) a linear regression controlling for party effects, and (3) matching to ensure balance on relevant covariates and fully get at the question of causality. We find that when the electoral system changes from PR to SMD, then legislators become significantly more constituency oriented in their voting behavior, indicated by increased levels of defections from the party line of voting. However, when the electoral system changes from SMD to PR, there is no significant change in the voting behavior of legislators. These asymmetric results are explained by the divergent ways in which the changes from one type of electoral system to the other alter the relative power of constituency versus the party over the reelection chances of legislators.
