Policy Adjustment by Parties in Response to Rival Parties’ Policy Shifts: Spatial Theory and the Dynamics of Party Competition in Twenty-Five Post-War Democracies

TLDR

Spatial theory suggests parties adjust policies in response to rivals, yet comparative evidence is limited. The study analyzes party policy programmes and opponents’ policies across 25 post‑war democracies using Comparative Manifesto Project data. Parties shift their positions in the same direction as rivals’ prior shifts, especially within ideological families, highlighting implications for spatial models, party dynamics, and representation.

Abstract

Although spatial theory posits that political parties adjust their policies in response to rival parties’ policy strategies, there is little comparative research that evaluates this hypothesis. Using the Comparative Manifesto Project data, we analyse the relationship between parties’ policy programmes and the policies of their opponents in twenty-five post-war democracies. The authors conclude that parties tended to shift their policy positions in the same direction that their opponents had shifted their policies at the previous election; furthermore, parties were particularly responsive to policy shifts by other members of their ‘ideological families’, i.e. leftist parties responded to other leftist parties while right-wing parties responded to right-wing parties. Their findings have important implications for spatial models of elections, for the dynamics of party systems and for political representation.