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Ideological Clarity in Multiparty Competition: A New Measure and Test Using Election Manifestos

  • James Lo, Sven-Oliver Proksch and Jonathan B. Slapin

Parties in advanced democracies take ideological positions as part of electoral competition, but some parties communicate their position more clearly than others. Existing research on democratic party competition has paid much attention to assessing partisan position taking in electoral manifestos, but it has largely overlooked how manifestos reflect the clarity of these positions. This article presents a scaling procedure that better reflects the data-generating process of party manifestos. This new estimator allows us to recover not only positional estimates, but also estimates for the ideological clarity or ambiguity of parties. The study validates its results using Monte Carlo tests, a manifesto-drafting simulation and a human coding exercise. Finally, the article applies the estimator to party manifestos in four multiparty democracies and demonstrates that ambiguity can enhance the appeal of parties with platforms that become more moderate, and lessen the appeal of parties with platforms that become more extreme.

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Princeton University; McGill University; University of Houston (emails:,, We wish to thank the many individuals who commented on earlier drafts of this article, including Ken Benoit, Will Lowe, Shawn Treier, several anonymous reviewers, and seminar participants at the University of Mannheim, Nuffield College, Oxford and Rice University. James Lo and Sven-Oliver Proksch gratefully acknowledge financial support for this project from the SFB 884 on the Political Economy of Reforms at the University of Mannheim (project C4), funded by the German Research Foundation. Replication materials and an online appendix are available at

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British Journal of Political Science
  • ISSN: 0007-1234
  • EISSN: 1469-2112
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