Amicus Coalition Heterogeneity and Signaling Credibility in Supreme Court Agenda Setting

What makes lobbying coalitions successful? We contend that greater preference heterogeneity among members of a lobbying coalition enhances the credibility of its signals to a target audience. To test this theory, we analyze the relationship between the preference heterogeneity of state amicus coalitions at the agenda setting stage and the probability of the U.S. Supreme Court granting review in state-filed cases. The results suggest that petitions are more likely to be granted as the preference heterogeneity among members of amicus coalitions increases. Our theoretical and empirical approaches are easily adapted to the study of lobbying influence in other institutional contexts.