Conventional explanations of the solicitor general's influence on the Supreme Court emphasize his expertise or experience. We articulate and test a more political account based on insights from signaling theory. We argue justices will be more receptive to signals from the solicitor general (S.G.) when either the justice and S.G. are ideologically proximate or the S.G.'s signal is contrary to his ideological predisposition. We test our account over the period from 1953 to 2002 using a newly developed interinstitutional measure of ideology that places executive and judicial actors on the same spatial scale. Our results highlight the political nature of the S.G.'s influence, challenging the received wisdom about the S.G.'s impact on the Supreme Court.