Individual Differences in Group Loyalty Predict Partisan Strength

The strength of an individual’s identification with their political party is a powerful predictor of their engagement with politics, voting behavior, and polarization. Partisanship is often characterized as primarily a social identity, rather than an expression of instrumental goals. Yet, it is unclear why some people develop strong partisan attachments while others do not. I argue that the moral foundation of Loyalty, which represents an individual difference in the tendency to hold strong group attachments, facilitates stronger partisan identification. Across two samples, including a national panel and a convenience sample, as well as multiple measures of the moral foundations, I demonstrate that the Loyalty foundation is a robust predictor of partisan strength. Moreover, I show that these effects cannot be explained by patriotism, ideological extremity, or directional effects on partisanship. Overall, the results provide further evidence for partisanship as a social identity, as well as insight into the sources of partisan strength.