From Bornforbattle74.....The US Constitution provides for replacing the President and Vice President in the event they are unable to discharge their duties....
FROM WIKIPEDIA6x6x6 is 216
Article II, Section 1, Clause 6 of the Constitution reads:
In Case of the Removal of the President from Office, or of his Death, Resignation, or Inability to discharge the Powers and Duties of the said Office, the Same shall devolve on the Vice President ...
This provision is ambiguous as to whether, in the enumerated circumstances, the vice president becomes the president, or merely assumes the "powers and duties" of the presidency. It also fails to define what constitutes inability, or how questions concerning inability are to be resolved.[3] The Twenty-fifth Amendment addresses these deficiencies.