This introductory essay provides a backdrop to frame the more specific insights of the contributors to this special issue. I open by assessing two key legacies in place at the time of the ACA’s passage: the health insurance regime and rising health care costs. The spotlight then turns to the ACA, zeroing in on several of its pivotal provisions. The sections that follow show how the ACA and related health care developments intersect with broader issues of governance: the rise of executive branch discretion within the nation’s separation of powers system, the increased importance of the administrative presidency, and the emergence of fractious federalism rooted in partisan polarization