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

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....