Measuring Partisanship as a Social Identity in Multi-Party Systems

There is no doubt that partisanship is a powerful influence on democratic political behavior. But there is also a lively debate on its nature and origins: Is it largely instrumental in nature and shaped by party performance and issues stances? Or is it basically a long-standing expressive identity reinforced by motivated reasoning and strong emotions? We assess the nature of partisanship in the European context, examining the measurement properties and predictive validity of a multi-item partisan identity scale included in national surveys conducted in the Netherlands, Sweden, and the U.K. Using a latent variable model, we show that an eight-item partisan identity scale provides greater information about partisan intensity than a standard single-item and has the same measurement properties across the three countries. In addition, the identity scale better predicts in-party voting and political participation than a measure of ideological intensity (based on both left-right self- placement and agreement with the party on key issues), providing support for an expressive approach to partisanship in several European democracies.