Holding two second-order elections simultaneously is expected to increase electoral participation. We exploit a natural experiment in which one group of Czech precincts was “as if” randomly assigned to holding subnational elections concurrently with senatorial ones. Using a unique data set containing variables on more than thirteen thousand precincts in five elections between 2000 and 2016, we detect a modest effect of concurrency only in the first election but no or inconsistent effect in the four subsequent contests. Furthermore, we report a strong effect of concurrency on invalid voting. We check for robustness using difference-in-differences design and matching techniques. Incongruent with existing theories, concurrency does not deliver on its promises and may come at a substantial cost to political representation. The surprising null effect on turnout is attributable to analyzing the effect of concurrency of the less salient on more salient elections.

同时举行两次二次选举预计将增加选举的参与度。我们利用了一个自然实验，其中一组捷克地区“好像”被随机分配给与地方选举同时举行的地方选举。在2000年至2016年之间的五个选举中，我们使用包含变量的独特数据集来对一万三千个选区进行了研究，我们仅在第一次选举中发现并发的适度影响，而在随后的四场竞赛中却没有或存在不一致的影响。此外，我们报告了并发对无效投票的强大影响。我们使用差异设计和匹配技术检查鲁棒性。与现有理论不一致，并发不能兑现其诺言，可能会给政治代表制带来巨大的代价。