The papal conclave from April 4-8, 1455 elected Alfonso Borja Pope Callixtus III following the death of Pope Nicholas III. The conclave was the first in the Apostolic Palace, the site of all but five papal conclave thereafter. The conclave was also the first to feature accessus voting (votes cast in accessit), derived from a practice of the Roman Senate, where a cardinal could change their vote after an unsuccessful scrutiny to any cardinal already receiving votes.