The Constitutional Topics pages at the USConstitution.net site are presented to delve deeper into topics than can be provided on the Glossary Page or in the FAQ pages. This Topic Page concerns the Presidential Line of Succession. The Line of Succession is mentioned in two places in the Constitution; in Article 2, Section 1, and the 25th Amendment. The Topic Page for the Presidential Disability is also of interest.
The 25th Amendment reiterates what is stated in Article 2, Section 1: that the Vice President is the direct successor of the President. He or she will become President if the President cannot serve for whatever reason. The 25th also provides for a President who is temporarily disabled, such as if the President has a surgical procedure or if he or she become mentally unstable.
The original Constitution provides that if neither the President nor Vice President can serve, the Congress shall provide law stating who is next in line. Currently that law exists as 3 USC 19, a section of the U.S. Code. This law was established as part of the Presidential Succession Act of 1947. There, the following line of succession is provided:
The only exception to the line provided in the law states that to ascend to the Presidency, the next person in line must be constitutionally eligible. Any person holding an office in the line of succession who, for example, is not a naturally-born citizen cannot become President. In this case, that person would be skipped and the next eligible person in the line would become President.
To see who holds these posts, see The Cabinet Topic Page.
Prior to 1947
In 1792, Congress passed the first presidential succession act. This act was fraught with political wrangling between the Federalists and Antifederalists, as much early U.S. policy was. The Federalists did not want the Secretary of State, since Thomas Jefferson held the position, and he was emerging as a leader to the Antifederalist camp. Some were wary of the President Pro Tem of the Senate, because of the apparent mixing of the branches of government so recently established. Ditto the House Speaker and the Chief Justice of the Supreme Court. The eventual compromise did include two persons to fall in line past the Vice President. The President Pro Tem of the Senate first, then the Speaker of the House.
The issue was taken up again in 1886, when the Congressional leadership was removed from the line and replaced with the Cabinet, with the Secretary of State falling first in line. Finally, the 1947 Act added the Speaker of the House and President Pro Tem back in the line (but reversed from the 1792 order).