Vice President of the United States the Twenty-fifth Amendment established a procedure for filling such a vacancy: This procedure has been implemented twice since the amendment came into force. The first instance occurred in 1973 following the October 10 resignation of Spiro Agnew, when Gerald Ford was nominated by President Richard Nixon and confirmed by Congress. The second occurred 10 months later following Ford's August 9, 1974 accession to the presidency upon Nixon's resignation, when Nelson Rockefeller was nominated by President Ford and confirmed by Congress. Had it not been for this new constitutional mechanism, the vice presidency would have remained vacant after Agnew's resignation and
Vice President of the United States practice, the presidential nominee has considerable influence on the decision, and in the 20th century it became customary for that person to select a preferred running mate, who is then nominated and accepted by the convention. In recent years, with the presidential nomination usually being a foregone conclusion as the result of the primary process, the selection of a vice presidential candidate is often announced prior to the actual balloting for the presidential candidate, and sometimes before the beginning of the convention itself. The first presidential aspirant to announce his selection for vice president before the beginning of the convention