Open/closed list and party choice: experimental evidence from the UK

Which parties benefit from open-list (as opposed to closed-list) proportional representation elections? This article shows that a move from closed-list to open-list competition is likely to be more favorable to parties with more internal disagreement on salient issues; this is because voters who might have voted for a unified party under closed lists may be drawn to specific candidates within internally divided parties under open lists. The study provides experimental evidence of this phenomenon in a hypothetical European Parliament election in the UK, in which using an open-list ballot would shift support from UKIP (the Eurosceptic party) to Eurosceptic candidates of the Conservative Party. The findings suggest that open-list ballots could restrict support for parties that primarily mobilize on a single issue.