This provision, side by side with the Twentieth and Twenty-fifth Amendments, is a major anchor for presidential succession in the United States. It provides, as supplemented by the Twenty-fifth Amendment, for the vice president to take over in the event of the removal, death, resignation, or inability of the president. It also authorizes Congress to establish a line of succession beyond the vice presidency. Left unclear by the clause was whether the vice president became president or simply acted as president in a case of succession.

Other ambiguities in the provision were noted at the Constitutional Convention by John Dickinson of Delaware, who asked, “[W]hat is the extent of the term ‘disability’ & who is to be the judge of it?” James Madison expressed concern that the provision would prevent the filling of a presidential vacancy by a special election, and he therefore successfully inserted the expression “until the Disability be removed, or a President shall be elected.” It is not clear whether this change was intended to apply when the vice president succeeded or only when an officer designated by Congress was called upon to serve in the case of a double vacancy. Nor is it clear whether after a special election the winner(s) serves a full four-year term. In any event, there has never been a special election for president, although the provision allowing for its possibility was included in the country’s early presidential succession laws.

A related question is whether “officers” when called on to serve were constitutionally required to retain their position during a period of service as acting president, as both James Madison and some current scholars opine. The 1792 statute seemed to indicate that when an “officer” became acting president, that officer retained his current position until a successor filled the presidential office. The current succession law of July 18, 1947, as amended, contemplates a resignation by statutory successors once they assume the powers of the presidency as acting president. That provision creates an issue as to whether in a case of presidential inability, it is appropriate to have an acting president who does not retain his or her existing office, and, in turn, whether legislative officers in line would violate the Incompatibility Clause of Article I, Section 6, Clause 2, which forbids a member of either House “during his Continuance in Office” from holding an “Office under the United States.”

In addition, serious constitutional questions remain regarding the “bumping” provision of the succession statute, which requires a statutory successor, in the case of cabinet members, to step down once a Speaker or president pro tempore becomes available. The “bumping” provision may run afoul of the requirement of the Presidential Succession Clause that “such Officer shall act accordingly [as acting president], until the Disability be removed, or a President shall be elected.”

Another ambiguity may be what kind of “officer” Congress can designate in a statute of presidential succession. The drafting history of Article II, Clause 1, Section 6 indicates that the Framers intended “officers of the United States” as the eligible category, but less clear is whether legislative leaders or legislators are included. Debate surrounding that issue has been a constant since the first succession law, with many scholars contending that neither the Speaker of the House of Representatives nor president pro tempore of the Senate is an officer in the sense contemplated by the Constitution. Proponents and opponents of this view cite provisions of the Constitution for support, such as Article I, Section 2, Clause 5 (Impeachment) and Article I, Section 6, Clause 2 (Sinecure Clause).

Both the First and Second Congresses debated who should be in the line of succession. The secretary of state, the chief justice, the president pro tempore of the senate, and the Speaker of the House of Representatives were all mentioned. On March 1, 1792, Congress resolved the issue by choosing the president pro tempore and the Speaker, respectively, prompting criticism from Madison and others that the congressional officers were not within the contemplation of the succession provision. No occasion called for the law to be implemented. Interestingly, at one point in history—when Chester A. Arthur succeeded to the presidency—there was no Speaker or president pro tempore, and therefore there was no one at all in the line of succession under the law of 1792. From 1886 until 1947, Congress included only cabinet members and not legislators in the line of succession, largely because of doubts whether legislators qualified as “officers.” The current succession statute, however, contains the legislative offices, with the Speaker first and the president pro tem next, followed by a line of cabinet officers in the order in which the executive departments were created.

In 1841, when President William Henry Harrison died in office, Vice President John Tyler assumed the presidency for the rest of the term. His claim to president, not simply vice president acting as president, drew criticism. The precedent he set, however, took and became the operating principle when other presidents died in office. These presidents were Zachary Taylor, Abraham Lincoln, James Garfield, William McKinley, Warren Harding, Franklin Roosevelt, and John Kennedy. On the other hand, Tyler’s example became a major obstacle for situations involving the temporary inability of a president because, under the wording of this clause, the status of a vice president in a case of death would appear to be the same as in a case of inability or resignation or removal. As a consequence, on a number of occasions vice presidents declined to consider relieving a disabled president because of the Tyler precedent and also because of the ambiguities first raised by John Dickinson. This was the case in 1881 when President James A. Garfield lay dying and some suggested that Vice President Chester A. Arthur take charge, and again in 1919 after President Woodrow Wilson’s stroke, when Vice President Thomas R. Marshall was urged to do the same. In 1967, the adoption of the Twenty-fifth Amendment eliminated much of the remaining uncertainties regarding presidential succession.