1268–1271 papal election
The 1268–1271 papal election (from November 1268 to 1 September 1271), following the death of Pope Clement IV, was the longest papal election in the history of the Catholic Church. This was due primarily to political infighting between the cardinals. The election of Teobaldo Visconti as Pope Gregory X was the first example of a papal election by "compromise", that is, by the appointment of a committee of six cardinals agreed to by the other remaining ten (this method was attempted once before, in the 1227 papal election, but the choice of the committee refused the honor and the full group of cardinals proceeded to elect the pope). The election occurred more than a year after the magistrates of Viterbo locked the cardinals in, reduced their rations to bread and water, and removed the roof of the Palazzo dei Papi di Viterbo where the election took place.