The decree of 1059 assumed that elections would be unanimous; so it made no provision for when a divided College could not agree on a candidate, leading to antipopes at virtually every election after 1059. In 1179 the Third Lateran Council required a two-thirds majority of all voting cardinals for election, if unanimity was impossible. Excommunication was mandated for those who refused to accept a pope elected by two-thirds majority.
But even two-thirds proved to be difficult to achieve in many elections after 1179. The most notorious began in 1268 at Viterbo, since it had become practice to hold the election where the pope had died. It is clear from the sources that the cardinals came and went between the cathedral and their homes in the first months of the election process. After fourteen months with no conclusion to the endless balloting (we do not know how often it took place),the cardinals allowed themselves to be locked in a palace. That failed to persuade them to agree on a pope. As the election slipped into 1270, the people of Viterbo began to put pressure on the cardinals, reaching the point of taking the roof off the palace.The people supposedly acted on a cardinal’s humorous comment that the roof should be removed to give free access to the Holy Spirit. The cardinals threatened to put the whole city under interdict, and a makeshift roof was put back on. The hardship of the long enclosure resulted in two cardinals dying and a third leaving because of ill health.Finally Gregory X was crowned after a vacancy of forty months.
The conclave, from the Latin cum clave,“with a key,”now became the process by which the pope was chosen. After his election Gregory issued a bull that required that the conclave begin ten days after the pope’s death normally in the same city where he died. The chief officers of the city where the conclave took place were obliged to see tha it was conducted properly. The cardinals would be locked in with two conclavists each.Once locked in,they could not communicate with the outside until the election was over except by the agreement of all. A turnstile was set in a window to pass food inside. Only a small amount of food would be provided per person, and there was a timetable for reducing the cardinals’ food and comfort level if the conclave dragged on. Imposing more urgency on the cardinals to finish their task was the rule that they could not draw their incomes during a conclave.The conclave would change only in details after 1274.
One purpose of the strict rules of conclave was to reduce the outside political pressure on the cardinals during the time they were involved in electing a pope, which in this era came more from the Roman nobility than the Catholic princes. More important, the rules were intended to persuade them to act quickly. They certainly were not meant to keep secret the details of the voting process once it was over. The new popes continued to write to the Catholic rulers, as they had been doing since about 1100, with the details of their elections. Accounts of the conclaves by those who participated, both cardinals and their conclavists, began to appear soon after the rules were created, as did chronicles written by outsiders who had sources within.
Sources: Baumgartner, Frederic J. (2003) I will observe absolute and perpetual secrecy”: The Historical Background of the Rigid Secrecy Found in Papal Election The Catholic Historical Review (89) 2, pp. 165-181