The U.S. government's expansive role in public policy is caught in a swirl of conflicting cross-currents. On the one hand, popular expectations about government's responsibility to solve problems often exceed the capacity of state and local authorities to respond effectively. On the other hand, policies developed at the national level may not sufficiently reflect the great diversity of interests across the U.S. to be effective at the local level. Moreover, the search for effective policy is further complicated by theoretical debates about the constitutional framework of federalism, e.g., what limits on national power can be derived from the Tenth Amendment?