The vice prefect of the Vatican Apostolic Library, Ambrogio Piazzoni, explained that the process by which a new Pope is chosen has undergone several changes in the past 100 years.
Offering a historical background on the conclaves, Piazzoni explained that in the year 1179, Pope Alexander III decreed that two-thirds of the vote was necessary in order for a papal election to be valid. In 1276, the first papal election was held behind closed doors, with Pope Innocent V emerging as Pontiff. In 1621, Pope Gregory XV established the requirement for a written secret vote.
The first conclave of the 20th century in 1903 resulted in the election of St. Pius X, with the new requirement that the documentation on the conclave and the various ballot scrutinies be kept in a file which only the Holy Father is allowed to view.
The conclave of 1914, which saw the election of Pope Benedict XV, “was the only time the votes were re-checked,” Piazzoni explained.
In this election, he said, “the number of votes in favor of the Pope was exactly two-thirds of the participants, and since it was invalid for a cardinal to vote for himself, the votes were reviewed to ensure Benedict XV had not voted for himself.”
Pope Pius XI decided in 1922 to extend the waiting period before a conclave could begin from 10 to 15 days in order to allow for cardinals living far away from Rome to arrive in time for the election.
In 1939, for the first time in centuries, all of the eligible cardinals took place in the conclave.
“There were 62 and they were all present. In two days and three ballots, Eugenia Pacelli, Pope Pius XII, was elected,” Piazzoni said.
In 1945, after World War II, Pius XII promulgated the constitution “Vacantis Apostolicae Sedis,” which established a series of new norms.
“Out of prudence, one more vote was required for a valid election beyond the two-thirds majority: so now it must be two-thirds plus one,” Piazzoni explained. “This meant that no controlling of the vote would be necessary because even if someone voted for himself, that vote would be the extra one.”
Another change dictated that as soon as the Chair of Peter was vacant, most of the cardinals in the Roman Curia cease in their functions, with just a few exceptions.
In 1958, Pope John XXIII was elected, and with his motu proprio, “Summi Pontificis Electio,” he established that notes made by the cardinals during the conclave could be archived, requiring that only the votes be burned.
Another important document, Pope Paul VI’s motu proprio, “Ingravescentem Aetatem,” was promulgated in 1970. It sets the age limit for voting in a conclave at 80. In 1978, Paul VI died and the largest conclave to date was held, with 111 cardinals.
Piazzoni recalled that “after four ballots Albino Luciani - John Paul I - was elected. He died 33 days later and obviously did not have time to make any laws regarding the conclave.”
“At the second conclave in 1978, there were eight ballots and Karol Wojtyla was finally elected.”
In 1986, Wojtyla – now Pope John Paul II – promulgated the document “Universi Dominici Gregis” with new norms for the conclave.
“One of its interesting innovations is that the location of the conclave is established: the Sistine Chapel,” Piazzoni said. “Another is that it establishes the place where the cardinals must stay: the St. Martha’s Residence.”
After his election in 2005, Pope Benedict XVI introduced another change to voting procedure in his document, “De Aliquibus Mutationibus in Normis De Electione Romani Pontificis.”
Revoking a provision from John Paul II’s “Universi Dominici Gregis,” Benedict XVI gave the Cardinal electors the faculty to elect the Roman Pontiff by an absolute majority in case of a deadlock.