An acting president of the United States is a person who lawfully exercises the powers and duties of the president of the United States despite not holding the office in their own right. There is an established presidential line of succession in which officials of the United States federal government may be called upon to be acting president if the incumbent president becomes incapacitated, dies, resigns, or is removed from office (by impeachment by the House of Representatives and subsequent conviction by the Senate) during their four-year term of office; or if a president-elect has not been chosen before Inauguration Day or has failed to qualify by that date.
Presidential succession is referred to multiple times in the U.S. Constitution: Article II, Section 1, Clause 6, the Twentieth Amendment, and the Twenty-fifth Amendment. The vice president is the only officeholder explicitly named in the Constitution as a presidential successor. The Article II succession clause authorizes Congress to designate which federal officeholders would accede to the presidency if the vice president were unable to do so, a situation which has never occurred. The current Presidential Succession Act was adopted in 1947 and last revised in 2006. The order of succession is as follows: the vice president, the speaker of the House of Representatives, the president pro tempore of the Senate, and then the eligible heads of the federal executive departments who form the president's Cabinet in the order of creation of the department, beginning with the secretary of state.
