If was against this backdrop that President Barack Obama signed the Patient Protection and Affordable Care Act in March 2010. As Secretary of Health and Human Services Kathleen Sebelius notes in this special issue, the new law constituted an epic policy breakthrough culminating a century of reform effort. The Affordable Care Act (or ACA) promised to insure more than 30 million people who lacked coverage. Under the most placid political circumstances, implementation of the ACA would pose thorny challenges for public administrators at all levels of the federal system. But the political context was anything but placid. The ACA prevailed with on Republican votes in Congress. Once passed, the law became a lightning rod for anger and intense ideological attacks. Many Republicans in Congress worked assiduously to derail implementation of the law as a first step toward its repeal. Meanwhile, state attorneys general filed suits to overturn the ACA in the courts. Several Republican governors vowed to do the minimum to implement the law. In sum, the ACA became the poster child for the well-documented trend toward “asymmetric partisan polarization” in the United States over the last several decades (e.g., Abramowitz 2010). This trend has featured some movement to the left among Democrats and a much more dramatic shift to the right among Republicans.