What explains preferential voting? A field experiment in Portugal

Abstract

This article analyzes the predictors of preferential voting in flexible list systems, focusing on political sophistication, voting rules and district size. It relies on a field experiment carried out in Portugal on the 2015 legislative election day. We
found that the effect of district size depends on the nature of the voting rules introduced (optional or compulsory preferential voting). Also, political interest tends to lose its significance when preferential voting is compulsory. Thus, preferential voting does not constitute an obstacle for those with less political sophistication to express a vote, especially when the voting rules make preferential voting compulsory.