Scholars have long treated the Twelfth Amendment as a constitutional obscurity, a merely mechanical adjustment to the electoral college—and perhaps a less than successful one at that. This consensus is mistaken. In fact, the Twelfth Amendment accomplished one of the most consequential changes to the structure of our constitutional government yet. It fundamentally altered the nature of the Executive and the Executive’s relationship to the other branches of government. The Amendment changed the Executive into something it had not been before: a political office. The presidency designed at Philadelphia was intended to be neither a policymaking nor a representative institution, but rather an apolitical office standing above partisan conflict. The Twelfth Amendment changed this design. It converted the electoral college into a form of public election, facilitating organized political competition for the presidency and linking the office to popular majorities. This revision of the electoral college had twin structural effects. First, the Amendment unified the executive branch under the political control of the President and made single-party control of the Executive a near certainty. Second, the Amendment changed the Executive’s relationship to Congress by conferring on the President new warrants for political action and a representative status it had not previously enjoyed. Together, these structural changes altered the very nature of the Executive—and along with it, the meaning of “executive power.” This Article concludes with a close analysis of the Amendment’s interpretive implications for contested questions of executive power, including the President’s power to remove subordinates, to conclude treaties and executive agreements, and to exercise directive authority over administrative agencies.