An acting president of the United States is an individual who legitimately exercises the powers and duties of the president of the United States even though that person does not hold 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 take on presidential responsibilities if the incumbent president becomes incapacitated, dies, resigns, 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, as well as the Twentieth Amendment and Twenty-fifth Amendment. The vice president is the only officeholder 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 in the event that 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, beginning with the secretary of state.
If the president dies, resigns or is removed from office, the vice president automatically becomes president. Likewise, were a president-elect to die during the transition period, or decline to serve, the vice president-elect would become president on Inauguration Day. A vice president can also become the acting president if the president becomes incapacitated. However, should the presidency and vice presidency both become vacant, the statutory successor called upon would not become president, but would only be acting as president. To date, two vice presidents—George H. W. Bush (once) and Dick Cheney (twice)—have served as acting president. No one lower in the presidential line of succession has so served.
The qualifications for acting president are the same as those for the office of president. Article II, Section 1, Clause 5 prescribes three eligibility requirements for the presidency. At the time of taking office, one must be a natural-born citizen of the United States, at least thirty-five years old, and a resident of the United States for at least fourteen years.
A person who meets these requirements may still be constitutionally disqualified from the presidency under any of the following conditions:
Article II, Section 1, Clause 6 makes the vice president first in the line of succession. It also empowers Congress to provide by law who would act as president in the case where neither the president nor the vice president were able to serve.
Two constitutional amendments elaborate on the subject of presidential succession and fill gaps exposed over time in the original provision:
On April 4, 1841, only one month after his inauguration, William Henry Harrison died. He was the first U.S. president to die in office. Afterward, a constitutional crisis ensued over the Constitution's ambiguous presidential succession provision (Article II, Section 1, Clause 6).
Shortly after Harrison's death, his Cabinet met and decided that John Tyler, Harrison's vice president, would assume the responsibilities of the presidency under the title "Vice-President acting President". Instead of accepting this proposed title, however, Tyler asserted that the Constitution gave him full and unqualified powers of the presidency and had himself sworn in as president; this set a critical precedent for the orderly transfer of power following a president's death. Nonetheless, several members of Congress, such as representative and former president John Quincy Adams, felt that Tyler should be a caretaker under the title of "acting president", or remain vice president in name. Senator Henry Clay saw Tyler as the "vice-president" and his presidency as a mere "regency".
Throughout Tyler remained resolute in his claim to the title of President and in his determination to exercise the full powers of the presidency. The precedent he set in 1841 was followed subsequently on seven occasions when an incumbent president died prior to the presidential succession being enshrined in the Constitution through section 1 of the Twenty-fifth Amendment.
Though the precedent regarding presidential succession due to the president's death was set, questions concerning presidential "inability" remained unanswered, such as what constituted an inability, who determined the existence of an inability, and did a vice president become president for the rest of the presidential term in the case of an inability or is the vice president merely "acting as president". Due to this lack of clarity, later vice presidents were hesitant to assert any role in cases of presidential inability.
On two occasions, in particular, the operations of the executive branch were hampered due to the fact that there was no constitutional basis for declaring that the president was unable to function:
Proposed by the 89th Congress and subsequently ratified by the states in 1967, the Twenty-fifth Amendment also established formal procedures for addressing instances of presidential disability and succession. Its Section 3, which allows the president to voluntarily transfer his authority to the vice president, has been invoked on three occasions by two presidents. (Section 4, which addresses the case of an incapacitated president who is unable or unwilling to issue voluntary declaration, has not been activated since the amendment came into force.)
Two vice presidents have so far served as acting president while the president underwent a medical procedure.