Congress paid nearly no attention to the Constitution when enacting the Affordable Care Act (ACA) in 2010. Legislative hearings and committee reports ignored the Constitution altogether; legislative debates largely did the same. This Essay both highlights Congress’s indifference to the Constitution when enacting the ACA and examines the reasons behind this legislative failure. In particular, this Essay advances three explanations. First, Congress is generally uninterested in “public goods” like constitutional interpretation. Second, the polarization of Democrats and Republicans in Congress further depresses Congress’s interest in thinking about the Constitution; instead, the majority party seeks to limit opportunities for the minority party to raise constitutional objections to legislation. Third, there is no federalism constituency in Congress that pushes lawmakers to take federalism into account when enacting legislation. For this very reason, Republican lawmakers almost always attacked the ACA on policy, rather than on constitutional, grounds. While embracing these three explanations, this Essay rejects a fourth explanation, namely, that lawmakers had no reason to know that the ACA would be subject to vigorous constitutional attack. Finally, this Essay argues that congressional disinterest in constitutional federalism supports the Supreme Court’s establishment of boundaries that limit Congress’s Commerce Clause power. At the same time, this Essay does not endorse the action– inaction distinction advanced by five Justices in the ACA decision.