It has become clear in the past week that the president is incapacitated and cannot discharge the duties of his office.

The 25th Amendment has a safeguard in place for situations like this:

"Whenever the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that he is unable to discharge the powers and duties of his office, and until he transmits to them a written declaration to the contrary, such powers and duties shall be discharged by the Vice President as Acting President."