Palazzo dei Papi di Viterbo, the roof of which was removed in an attempt to speed up the election
Palazzo dei Papi di Viterbo, the roof of which was removed in an attempt to speed up the election

The papal election from November 1268 to September 1, 1271, following the death of Pope Clement IV, was the longest papal election in the history of the Roman Catholic Church. The election of Tebaldo Visconti as Pope Gregory X, the first example of a papal election by "Compromise," was effected by a Committee of six cardinals agreed to by the other remaining ten, occurred more than a year after the magistrates of Viterbo locked the cardinals in, reduced their rations to bread and water, and legendarily removed the roof of the Palazzo dei Papi di Viterbo.As a result of the length of the election, during which three of the twenty cardinal-electors died and one resigned, Gregory X promulgated the apostolic constitution, Ubi periculum, on July 7, 1274 (or 16), during the Second Council of Lyon, establishing the papal conclave, whose rules were based on the tactics employed against the cardinals in Viterbo. The election itself is sometimes viewed as the first conclave.
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