Presidential line of succession

The United States presidential line of succession is the order in which persons may become or act as President of the United States 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). The line of succession is set by the United States Constitution and the Presidential Succession Act of 1947 as subsequently amended to include newly created cabinet offices. The succession follows the order of Vice President, Speaker of the House of Representatives, President pro tempore of the Senate, and then the heads of federal executive departments who form the Cabinet of the United States. The Cabinet currently has fifteen members, beginning with the Secretary of State, and followed by the rest in the order of their positions' creation. Those heads of department who are ineligible to act as President are also ineligible to succeed the President by succession, for example most commonly if they are not a natural-born U.S. citizen.

Several constitutional law experts have raised questions as to the constitutionality of the provisions that the Speaker of the House and the President pro tempore of the Senate succeed to the presidency, and in 2003 the Continuity of Government Commission raised a number of other issues with the current line of succession.

...
Wikipedia