The original Presidential Succession Clause of the Constitution (Article II, Section 1, Clause 6) appeared to be relatively simple in providing for succession to the presidency. There were, however, troubling ambiguities. What was the meaning of “inability” of a president “to discharge the Powers and Duties of said Office”? Who determined the existence of an “inability”? Did a vice president become president for the rest of the presidential term in the case of an inability or in the event of death, resignation, or removal; or was he merely “acting as President”? It was clear that there was no procedure for filling a vacancy in the office of vice president, although the Constitution authorized Congress to legislate a line of succession to cover situations involving the death, resignation, removal, or inability of both the president and vice president.

Until the Twenty-fifth Amendment was adopted, the nation confronted a number of deaths in office of presidents and vice presidents, as well as periods when presidents were disabled. When President William Henry Harrison died in 1841, Vice President John Tyler, asserting that he was fully the president, ascended to the presidency for the rest of the term, claiming that was the proper interpretation of the clause. He insisted that he was “President,” not “Acting President.” The precedent he established by assumption of the presidency was followed by other vice presidents when presidents died in office. These presidents were Zachary Taylor, Abraham Lincoln, James A. Garfield, William McKinley, Warren G. Harding, Franklin D. Roosevelt, and John F. Kennedy. The vice presidents who succeeded to the office were Tyler, Millard Fillmore, Andrew Johnson, Chester A. Arthur, Theodore Roosevelt, Calvin Coolidge, Harry S. Truman, and Lyndon B. Johnson, respectively.

Although the Tyler precedent was helpful in providing for continuity and stability, it caused future vice presidents to hesitate in asserting any role in a case of presidential inability as opposed to the death of the president. There was the question of whether the vice president succeeded to the presidency for the rest of the term, even in a case of temporary inability, as well as the problem of the vice president’s being seen as a usurper because of the constitutional silence about his role in determining whether there was an inability. This hesitancy occurred during the eighty days when President Garfield lay dying after being shot by an assassin in 1881, in the period after President Woodrow Wilson suffered a stroke in 1919, and when President Dwight D. Eisenhower suffered a heart attack, an attack of ileitis, and then a stroke. To cope with any future inability, President Eisenhower and Vice President Richard M. Nixon developed an informal protocol. Although it did not have the force of law, it gave assurance that a case of inability would be handled with due regard for stability. It provided for the president to declare his own inability and, if unable to do so, enabled the vice president, with appropriate consultation, to make the decision. In either event, the vice president served as acting president until the president recovered his powers and duties upon his own declaration of recovery. This protocol was followed in turn by President Kennedy and Vice President Johnson and then by President Johnson and Speaker John McCormack. President Johnson and Vice President Hubert Humphrey orally agreed to a similar arrangement, though they executed no written letter of agreement.

Compounding the problem of presidential inability was the problem of vice presidential vacancy. Such a vacancy occurred whenever a president died in office, on the seven occasions when vice presidents died in office, and when Vice President John C. Calhoun resigned in 1832. In the absence of a mechanism for filling a vacancy, a statutory line of succession provided the necessary backup. This line changed twice in the country’s history. The original line, reflected in a law of 1792, placed the president pro tempore of the Senate next in line after the vice president. In 1886 the secretary of state was made first in line, followed by other members of the cabinet. Then, in 1947, the Speaker of the House of Representatives and president pro tempore of the Senate, respectively, were placed ahead of the secretary of state and all the other cabinet officers in line, now ending with the secretary of homeland security.

After President John F. Kennedy was assassinated in 1963, there was a movement to constitutionalize these practices and to provide more certainty. The Twenty-fifth Amendment reflects the history of succession in its provisions providing for the vice president to become president in the event of the death, resignation, or removal of the president and to serve as acting president for the duration of any inability. It allows a president to declare his own inability and resume his powers and duties when it has ended. This provision has been used when presidents underwent surgery—in 1985 by President Ronald Reagan and in 2002 and 2007 by President George W. Bush. The transfer of presidential power to their vice presidents was of short duration in each case. On other occasions in the administrations of both President George H. W. Bush and William J. Clinton, when the president underwent a medical procedure, consideration among the presidential staff was given to whether he should invoke Section 3 of the Amendment, but as neither president underwent general anesthesia, the need did not arise.

The president’s discretion in determining his own inability under Section 3 is broad. The discretion of those other officials whom Section 4 empowers to declare the president disabled, however, is more constrained. Section 4 was designed to cover cases where the president was unable to make or communicate a decision as to his competency. In those situations, the vice president with a majority of the cabinet, could declare the president unable to execute his office, whereupon the vice president would become acting president. However, if the president disagrees with the vice president and a majority of the cabinet, and the vice president and the cabinet renew their assertion of his inability, then Congress resolves the issue. The amendment also gives Congress the power to replace the cabinet and substitute another body to function with the vice president under Section 4.

It was not an accident that the amendment did not define “inability.” It was intended principally to cover cases of both physical and mental inability, such as when a president undergoes surgery, is kidnapped, or becomes infirm. It does not cover political and policy differences or poor judgment, incompetence, laziness, and the like.

The amendment, recognizing the importance of the vice presidency, added a Section 2 procedure for filling a vacancy in that office, namely, nomination by the president and confirmation by both houses of Congress. This procedure was used when Vice President Spiro T. Agnew resigned and was replaced by Gerald R. Ford and again after Richard M. Nixon resigned as president. Ford became president and Nelson A. Rockefeller became vice president by the same process. President Ford’s succession to the presidency was by virtue of Section 1 of the amendment and not based on the Tyler precedent.

Since 1967, there have been many meetings and studies to consider proposals to improve the system of presidential succession including the following: Congressional hearings in 1994, 2003, and 2004; a commission on presidential disability, the Miller Commission of the University of Virginia, which in 1988 proposed guidelines for advance planning by presidents; a Working Group on Presidential Disability, hosted by The Carter Center of Emory University and Wake Forest University, which focused on the role of doctors in cases of presidential inability; and studies and recommendations by the Continuity in Government Commission and a Presidential Succession Clinic at Fordham Law School with respect to gaps and ambiguities in the system, such as where there was no vice president, or the president and vice president were disabled at the same time, or a statutory successor acting as president became disabled.