The federal bureaucracy played a critical role in implementing most aspects of the Affordable Care Act's private insurance coverage expansion. Through brief case studies, the authors review three dimensions of this role: the development of the Center for Consumer Information and Insurance Oversight, rulemaking in the formulation of the essential health benefits package, and the implementation of the federal website. They relate these to themes in the public administration literature. Politics—both through state decisions and through continuing congressional action (and inaction)—pervaded the implementation process. The challenges of staffing and situating the new bureaucracy effectively changed vertical boundaries within the Department of Health and Human Services, with long-lasting consequences. Finally, the complex design of the policy itself made passage of the legislation easier but implementation much more difficult. Ultimately, however, implementation was remarkably successful, achieving improvements in coverage consistent with the Congressional Budget Office's projections.