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.
The early defeat of Greek Cardinal Basilios Bessarion—a potential compromise candidate between the Colonna and Orsini factions—is a notable display of the lingering antipathy towards certain characteristics of the Eastern church, such as bearded priests, centuries after the East-West Schism. Although Western canon law had prohibited beards for priests since at least the eleventh century, the issue would continue to be debated well into the sixteenth century.
The two main factions of the cardinals were divided between the followers of Prospero Colonna and Latino Orsini; among the papabile were Barbo, Trevisan, Capranica, Orsini, and Bessarion. Capranica received a plurality on the first three scrutinies, with the other votes scattered; Orsini and the French cardinals rallied against Capranica because he was close to Colonna.
On April 6, Easter Sunday, the factions began to consider neutral candidates. In this capacity, Basilios Bessarion (noted for defecting from the Eastern Church following the East–West Schism) was able to receive eight votes, before his candidacy was scuttled following a speech by Alain de Coëtivy—recorded by eyewitnesses—which emphasized Bessarion's former membership in the Eastern Orthodox Church and his retention of Greek mannerisms, such as a full beard. The French cardinal is reported to have remarked:
- "Shall we select for Pope, for head of the Latin Church, a Greek, a mere interloper? Bessarion still wears his beard—and forsooth, he is to be our Lord! How poor, then, must be our Latin Church, if we can find no worthy man in it, but must needs resort to a Greek, and to one, too, who but yesterday attacked the Roman faith! And because he has now returned shall he be our master and the leader of the Christian army? Behold, such is the poverty of the Latin Church that she cannot find an apostolic sovereign without resorting to a Greek! Oh, Fathers! Do what you think fit; but for myself and those who think with me, we will never consent to a Greek head of the Church!"
Bessarion made no attempt to defend himself, claiming he was not interested in being elected; his reputations for reform and austerity also would have been unpopular with many of the Renaissance cardinals. Nevertheless, the renowned humanist scholar remained a strong candidate in the following 1464 conclave as well.
It is known that the early scrutinies the following Monday were disorganized; for example, non-cardinal Antonio de Montefalcone received at least one vote. de Coëtivy and Trevisan pushed for Borja's election, gaining momentum until Borja prevailed the following Tuesday. The core of the requisite two-thirds majority was likely composed of the French, Spanish, and Venetian cardinals: Trevisan, de Coëtivy, Barbo, Orsini, d'Estaing, de Carvajal, de La Cerda, Rolin, and Torquemada; the vote of Isidore or Calandrini, or both, likely was also required as Borja very likely did not vote for himself; Borja almost certainly did not receive the votes of Colonna, Capranica, or Bessarion.
|Giorgio Fieschi||Ligurian||Cardinal-bishop||Bishop of Palestrina||18 December 1439||Eugenius IV||Dean of the College of Cardinals; bishop of Albenga|
|Isidore of Kiev||Greek||Cardinal-bishop||Bishop of Sabina||18 December 1439||Eugenius IV||Archbishop of Ruthenia|
|Basilios Bessarion||Greek||Cardinal-bishop||Bishop of Frascati||18 December 1439||Eugenius IV||Latin Patriarch of Jerusalem; administrator of Mazara del Vallo; legate in Bologna|
|Alfonso Borja||Spanish||Cardinal-priest||Title of Ss. IV Coronati, bishop of Valencia||2 May 1444||Eugenius IV||Elected Pope Callixtus III|
|Juan de Torquemada, O.P.||Spanish||Cardinal-priest||Title of S. Maria in Trastevere||18 December 1439||Eugenius IV|
|Lodovico Trevisan||Venetian||Cardinal-priest||Title of S. Lorenzo in Damaso, patriarch of Aquileia||1 July 1440||Eugenius IV||Camerlengo of the Holy Roman Church|
|Pietro Barbo||Venetian||Cardinal-priest||Title of S. Marco||1 July 1440||Eugenius IV||Future Pope Paul II; cardinal-nephew;bishop of Vicenza; archpriest of the Vatican Basilica|
|Juan Carvajal||Spanish||Cardinal-priest||Title of S. Angelo in Pescheria, bishop of Plasencia||16 December 1446||Eugenius IV|
|Antonio Cerdà i Lloscos, O.SS.T.||Spanish||Cardinal-priest||Title of S. Crisogono, bishop of Lérida||16 February 1448||Nicholas V|
|Latino Orsini||Roman||Cardinal-priest||Title of Ss. Giovanni e Paolo||20 December 1448||Nicholas V||Administrator of the see of Bari|
|Alain de Coëtivy||French||Cardinal-priest||Title of S. Prassede, bishop of Avignon||20 December 1448||Nicholas V||Administrator of the see of Nimes|
|Filippo Calandrini||Ligurian||Cardinal-priest||Title of S. Susanna, bishop of Bologna||20 December 1448||Nicholas V||Cardinal-nephew; camerlengo of the Sacred College of Cardinals|
|Guillaume d'Estaing, O.S.B.||French||Cardinal-priest||Title of S. Sabina||19 December 1449||Nicholas V||Bishop of Fréjus|
|Domenico Capranica||Capranica Prenestina||Cardinal-priest||Title of S. Croce in Gerusalemme, administrator of Fermo||23 July 1423 (in pectore, admitted into Sacred College on 30 April 1434)||Martin V (confirmed by Eugenius IV)||Protopriest; archpriest of the Lateran Basilica; grand penitentiary|
|Prospero Colonna||Roman||Cardinal-deacon||Deacon of S. Giorgio in Velabro||24 May 1426||Martin V||Protodeacon|
|Peter of Foix, O.F.M.||French||Cardinal-bishop||Bishop of Albano||September 1414||Antipope John XXIII||Legate in Avignon; administratort of the sees of Arles and Dax|
|Guillaume d'Estouteville, O.S.B.Clun.||French||Cardinal-bishop||Bishop of Porto e Santa Rufina, archbishop of Rouen||18 December 1439||Eugenius IV||Papal legate in France; archpriest of the Liberian Basilica; administrator of Saint-Jean-de-Maurienne|
|Peter von Schaumberg||Germany||Cardinal-priest||Title of S. Vitale, bishop of Augsburg||18 December 1439||Eugenius IV|
|Dénes Szécsi||Hungarian||Cardinal-priest||Title of S. Ciriaco, archbishop of Esztergom||18 December 1439||Chancellor of the Kingdom of Hungary|
|Jean Rolin||French||Cardinal-priest||Title of S. Stefano al Monte Celio, bishop of Autun||20 December 1448||Nicholas V|
|Nicholas of Kues||German||Cardinal-priest||Title of S. Pietro in Vincoli||20 December 1448||Nicholas V||Bishop of Brixen|
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