| Abstract: | How do interest groups influence U.S. Supreme Court justices to vote in favor of their preferred outcomes? Following prior research on the influence of the Solicitor General, we develop and expand on the signaling theory of interest group influence via amicus curie briefs. We argue that an interest group's ideological reputation and the nature of the ideological signal it sends in its brief both function as powerful heuristics that convey information to the justices depending on the justices' own ideological preferences. When an organization files an amicus brief advocating for an outcome seemingly contrary to its traditional preferences (i.e., an unexpected signal), this signal should be more noticeable and credible than a signal in accordance with a group's conventional views (i.e., an expected signal). However, unexpected signals should have greater influence on justices who share the brief filer's preferences. We test our signaling theory on the terms from 1991 through 2002. We find that unexpected signals (but not expected signals) are associated with Supreme Court voting, and the influence of unexpected signals appears to be particularly strong among justices who share the ideological preferences of the brief filer. |
