This study examines the effect of district magnitude (DM) on electoral participation through a subnational analysis of Chile’s electoral reform. Chile’s transition from a binomial system (DM of 2) to a more proportional representation system (DM ranging from 3 to 8) offers a unique context to test voter mobilisation theories and explore non-linear relationships between DM and turnout. The findings reveal a heterogeneous impact of DM on voter turnout.

In highly competitive districts under the binomial system, turnout decreased post-reform, while in less competitive districts, it increased. A quadratic effect was also observed: participation increased up to a threshold of 4–5 seats but declined beyond that, suggesting a cognitive burden for voters in larger districts. These results contribute to the broader literature by offering empirical evidence from a non-industrialised democracy undergoing significant electoral reform, highlighting the importance of district competitiveness and the non-linear effects of DM on voter engagement.

Nerea C. Palma holds a Ph.D. in Political Science from the Pontificia Universidad Católica de Chile, with specialisations in Comparative Politics and Research Methods. Her research focuses on public opinion and electoral behavior, particularly political participation, satisfaction with democracy, and political disaffection.