In its early years, the church appears to have sought to curb outside influence by letting popes choose their own successors. But it wasn't possible to insulate the process for long. Soon, clergy and citizens of Rome were selecting the pope. He is, after all, the bishop of Rome as well as head of the church.
Factional tensions sometimes led to confusion and even violence. The history books show that Callistus I, a 3rd-century pope known for forgiveness of sinners, was opposed by a rival, Hippolytus, who was elected separately by conservative Christians who felt that prostitutes and usurers did not belong in the church. In any case, both Callistus and Hippolytus ran afoul of a Roman emperor: Callistus was executed and thrown into a well; Hippolytus was exiled to Sardinia and died there.
Profiles: List of cardinals whom Vatican observers consider to be papabili, or potential popes.
In A.D. 366, mob violence marred the election of Damasus I. Followers of rival candidates assaulted each other's churches. Hundreds of partisans died.
In later centuries, kings and emperors worked with purse and sword to influence the selection and control of popes. Byzantine emperors claimed the right to ratify papal selection, and kings of France and Spain forced popes to let them name "cardinals of the crown" so that the kings could command their own potential candidates and blocs of votes.
Families sometimes dominated the selection. One medieval pope was reputed to be the product of an affair between a predecessor and the 13-year-old daughter of a powerful family patriarch.
Gradually a system came into place whereby cardinals elected the pope. Beginning in 1179, the church decreed that this must be done by a two-thirds majority. That basic system lasted until this conclave and has often contributed to multiple inconclusive votes, given the difficulty of getting such a large number of voters to agree on one candidate.
Because of the changes instituted by John Paul, politicking may be rendered obsolete. "There is no longer an incentive to compromise and find a consensus candidate," wrote the Rev. Thomas J. Reese, a Jesuit priest, in his book "Inside the Vatican." "This change increases the likelihood of a more radical and ideological candidate being elected pope. It means that a pope can be elected who was opposed by just under half the cardinals." John Paul gave no reason for the change.
In any case, the voting cardinals this time will print the name of their choice on personal rectangular cards. The phrase "I elect as supreme pontiff" will be printed at the top in Latin. The electors are advised to disguise their handwriting.
In silence, each will approach an altar, on which will stand a chalice covered by a plate. The voter will kneel, say a short prayer, then declare, "I call as my witness Christ the Lord who will be my judge, that my vote is given to the one who before God should be elected." He will then put the folded ballot onto the plate, lift the plate to show the group there is just one ballot, then drop the ballot into the chalice. For all the oath-taking and invoking of the Holy Spirit, there remain worries about cheating.
When votes legitimately produce a deadlock, the ballots will be burned, with chemicals added to produce black smoke that will vent up a chimney, and by its color, signal the state of play to people outside.
When a winner emerges, the other cardinals will move to greet him. They used to kneel and kiss his hand as he sat, but John Paul did away with the practice -- he greeted the cardinals standing, embracing them. His predecessor, John Paul I, had ended the custom of the new pontiff being crowned with a tiara.
The outside world will only be able to imagine all of this. The public will be informed of a successful selection by the color of the smoke from the final ballots burning, this time white.
When John Paul I was elected, someone was confused about the chemical mixture and the smoke came out gray. No one knows exactly how it happened. It's a secret.