The vice-president becomes president if the presidency is vacated.
The 25th amendment specifies that the President may appoint a Vice President to fill a vacancy in that office, subject to the approval of both houses of Congress.
Order of succession.
Presidential Line of Succession
There is only one way to fill a vacancy in the vice-presidency as is specified in Amendment 25. The President selects a candidate and if both houses of Congress approve, he is the VP. Otherwise, the President makes another selection who must be approved. The process continues until Congress approves someone selected by the President.
William H. Rehnquist
The President can never appoint someone to fill a Senate vacancy. The U.S. Constitution allows the Governor of the state to which the vacant seat is entitled to make a temporary appointment to fill the seat until a special election can be held, but only if the state legislature has passed a bill allowing him/her to do so. Actually there is one Senate vacancy for which the President appoints a replacement: the U.S. Vice President, who constitutionally is also the President of the Senate. Vice presidential appointments require the approval of both houses of Congress.
If the president and vice-president both were unable to function, the Speaker of the House would be sworn in as President.
Amendment 25, section 2, established a procedure for filling a vacancy in the vice-presidency.
Richard Nixon appointed Gerald Ford to the VP position after Spiro Agnew resigned. This was the first VP vacancy that occurred after the ratification of the 25th amendment which gave the president the power to appoint a new VP if the office became vacant.
In the event of a vacancy in the presidency the vice president shall step in and perform the duties of the president. If the vice president is unable to hold this position then the next person in line would be the Speaker of the House of Representatives.
they call for a special election to fill the vacancy.
25th