Scholars often assert that public support for judicial authority induces Congress to grant resources and discretion to the Supreme Court. However, the theory of competing public agency embraced by the Constitution suggests that public support for courts cannot, by itself, explain congressional support for judicial authority. Instead, the logic of the separation of powers system indicates that legislative support for the institutional capacity of courts will be a function of public confidence in the legislature as well as evaluations of the judiciary. We test this theory, finding that public confidence in both Congress and the Court significantly affect congressional support for the Supreme Court, controlling for the ideological distance between the Court and Congress as well as the Court’s workload. The results offer a more refined and complex view of the role of public sentiment in balancing institutional power in American politics.