Adapt or Perish? How Parties Respond to Party System Saturation in 21 Western Democracies, 1945-2011

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This study examines whether (and how) parties adapt to party system saturation (PSS). A party system is oversaturated when a higher effective number of parties contests elections than predicted. Previous research has shown that parties are more likely to exit when party systems are oversaturated. This article examines whether parties will adapt by increasing the nicheness of their policy platform, by forming electoral alliances or by merging. Based on time-series analyses of 522 parties contesting 357 elections in twenty-one established Western democracies between 1945 and 2011, the study finds that parties are more likely to enter - and less likely to leave - electoral alliances if PSS increases. Additionally, a small share of older parties will merge. The results highlight parties' limited capacity to adapt to their environments, which has important implications for the literature on party (system) change and models of electoral competition.

Original languageEnglish
Pages (from-to)16-38
Number of pages23
JournalBritish Journal of Political Science
Issue number1
Early online date23 Aug 2019
Publication statusPublished - 2021


We would like to thank Tarik Abou-Chadi, Joost Berkhout, Marcel Hanegraaff, Bonnie Meguid, Pieter Moens, Gijs Schumacher, Floris Vermeulen, the four anonymous reviewers and the editor for their useful comments. This research was supported by Marc van de Wardt's postdoctoral research grant from the Research Foundation Flanders ‘FWO’ (FWP17/PDO/198).

FundersFunder number
Marc van de Wardt
Fonds Wetenschappelijk OnderzoekFWP17/PDO/198


    • electoral alliances
    • party change
    • party mergers
    • party platform change
    • political parties


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