This article provides the first systematic account of the relationship between campaign finance and federalism. Federalism — a fundamental characteristic of the constitutional structure — depends for its stability on political mechanisms. States and their advocates and representatives in Congress, federal agencies, political parties, intergovernmental lobbying groups, and other political forums work together to check federal interference with state governments. Entire normative theories of federalism depend on the assumption that this system of political safeguards is working effectively in the background. But the federalism and constitutional theory literatures lack a rigorous account of the effects of dramatic political change on pro-federalism political dynamics. Building that account is particularly timely now. Political safeguards work only if states retain significant political influence. But, as recent elections vividly demonstrate, Citizens United has created a new class of political operators — of which Super PACs are emblematic — whose potential political influence may be limitless. This article’s thesis is that Super PACs have the capacity to undermine all conventional political safeguards of federalism, pushing states far enough down the hierarchy of political influence to dramatically reshape the our system of government. This highlights the underappreciated extent to which Citizens United may have long-term structural consequences other than its effects on democratic representation. These developments have significant normative implications for federalism theory — at a minimum, they require reexamining the common assumption, central to numerous normative claims, that national political process is a durable channel for state self-defense. They also suggest new normative claims concerning campaign finance doctrine. If sustaining federalism is a compelling governmental interest, then federalism problems may justify new campaign spending restrictions despite the First Amendment and the reasoning of Citizens United, which otherwise appear to preclude further reforms.