American federalism contemplates that states will retain a significant degree of autonomy so that state power can serve as a meaningful counterweight to national power. It is often said that states exercise this function through extraconstitutional processes centered on the political party system. That is, states influence the content of national law and protect themselves from undesirable exercises of national power by using the mechanisms of internal party processes. If this process is to work properly, however, states must retain considerable political autonomy, for the possibility of state objection to exercises of national power is merely theoretical if state political processes are not sufficiently independent of their national counterparts to enable the state to adopt and assert ends or interests different from those asserted by the national government.
The evidence, however, suggests strongly that the growth of national political parties during and since the early nineteenth century created a two-way street. Parties not only offered states a way to influence national politics, but also created a reverse pathway by which national politics could influence, and in many cases overawe, any independent state-level politics. As a result, the same extraconstitutional pathways that provided states a means to protect themselves from national domination simultaneously eroded the political autonomy necessary for states to maintain the kind of independent wills contemplated by the federal arrangement. This does not mean that states lack entirely the capacity to stand up to the federal government, but it does mean that their ability to do so is limited, not necessarily for lack of power but for lack of autonomous control over their political agendas and positions. This in turn suggests a much chastened conception of what it might mean for a subnational government to have the ability to “check” national power.