Vatican experts and some church leaders said that Benedict's decision holds the potential to set limits for future popes, to make them more subject to pressure from critics and to feed the perception that they are not just spiritual leaders of the world's 1.2 billion Roman Catholics but chief executives managing the vast multinational conglomerate that is the church, with its franchises around the globe and headquarters in the Vatican state.
"If Jack Welch looked like this wonderful 85-year-old gentleman and he stepped down, wouldn't you say, 'Bravo, Jack?' " said Cardinal Edward M. Egan, the retired archbishop of New York, who called Benedict's decision the sensible and logical thing to do. He was one of many cardinals to rally publicly around Benedict's choice, a radical step for an otherwise deeply conservative theologian.
Now as 115 cardinals gather here to elect a new pope, with initial meetings on Monday to decide the conclave's date, Benedict's decision confronts them, and will confront future popes, with a host of new factors.
The possibility of resignation could allow the cardinals to choose a younger man, knowing that a limited term is an option, or an older one, knowing that he could quit if he felt unable to fulfill his duties. It could lead to pressure on successors — driven by scandals, unpopular decisions or illness — to step down. Such pressure, or even the possibility of it, could affect how a pope makes decisions, some church officials fear.
"The precedent has been set," Cardinal Wilfrid F. Napier, the archbishop of Durban, South Africa, said in an interview on Friday. "If there were a pope to come into the situation that the good of the church requires some action and that action requires his resignation, he would look back at what Benedict did and say, 'It's an option I must consider, for the benefit of the church.' " He emphasized that in Benedict's case, health was the reason.
Such issues have never been on the table during the modern papacy. Not everyone is pleased about it, and some worry about a destabilizing effect.
In interviews last week, several cardinals referred to the possibility that papal critics could be emboldened now that resignation is on the table.
"What I would not like to see happen is that a pope would feel that there's almost a polling process — 'How's this going over? Am I effective?' " said Cardinal Timothy M. Dolan, the archbishop of New York. "That would not be good for the church."
Cardinal George Pell, the archbishop of Sydney, Australia, suggested in an interview with the Seven network in Australia that Benedict's example could prompt those who disagree with a pope to "mount a future campaign to get him to resign."
Popes in the past, including Benedict when he was Cardinal Joseph Ratzinger, have mused about the concept of resignation. Canon law and Pope John Paul II's rules for papal transition, established in 1996, also mention it. Church rules require the decision to be made "freely."
In his announcement on Feb. 11 and in speeches since, Benedict emphasized that he was stepping down because he felt his mental and physical powers had waned, making him not up to the job.
"In these last months I have felt that my strength had diminished," he told 150,000 people in St. Peter's Square on Wednesday in his valedictory address. His decision was "for the good of the church," he said, and indeed made freely.
Benedict, when he was Cardinal Ratzinger, watched as his predecessor and close collaborator, John Paul, grew increasingly infirm in the final years of his papacy, an experience believed to have weighed on Benedict's decision. His successors, however, may receive help in making such a decision.
"Now that Benedict has resigned for health reasons, future popes can be suggested to resign for health or other reasons by their staff, by senior cardinals in the curia," said Nicholas P. Cafardi, a civil and canon lawyer and former dean of Duquesne University School of Law. "This time it was clearly Benedict's call, but that might not always be exactly the case in the future."
Some cardinals are said to favor lifetime appointments and will seek a promise that the next pope will not step down, the Italian newspaper Corriere della Sera reported Friday. The very suggestion indicates that Benedict's decision has divided church leaders.
But Cardinal Napier of South Africa rejected the possibility that fellow eminences might seek such a commitment. To do so would be an implicit criticism of Benedict's decision, he said — very bad form in papal circles. He also emphasized that he believed that Benedict's decision was motivated by his condition, not by the turbulence that dogged his papacy.
Clerical sexual scandals around the world and what critics see as the church's inadequate response have roiled his tenure, along with allegations of widespread corruption and mismanagement in the Vatican. Benedict had also angered Jews, Muslims and Anglicans with his remarks.
One of the fundamentals of conclave handicapping is the question of age, and the new paradigm cuts both ways.
"I can see the conclave deciding to elect an older man, realizing he would not have to carry this burden into his 90s," Cardinal Sean P. O'Malley, the archbishop of Boston, told reporters on Thursday. "If he felt incapacitated, he would feel permission to resign."
Modern popes have an "extraordinarily demanding job" in an age when people are living longer, Cardinal O'Malley said. They are expected to travel extensively, deal with a sprawling bureaucracy and serve a globalized church in an era of hyperconnectivity, he noted.
At the same time, the cardinals may opt for a younger man with a resignation in his future, easing past fears of overly long papacies. Bishops, after all, are required to submit resignations at 75, and cardinals 80 and over (like Cardinal Egan, who reached that age last year) cannot vote in the conclave.
Eamon Duffy of the University of Cambridge, a historian of the history of Christianity, recalled that Cardinal John Henry Newman, the 19th-century cleric and intellectual whom Benedict beatified in 2010, once said that a pope should not serve longer than 20 years in office "because then they become gods and no one contradicts them."
Now, the cardinals "might be braver about choosing young men, and it gives people freedom to look at the job as something that they do for a period of time," Mr. Duffy said.
For better or worse, Benedict's resignation has wrought a fundamental change in the perception of the office. The church holds the pope to be the vicar of Jesus Christ and the direct successor of St. Peter.
"The effect will be to desacralize the figure of the pope," said Paolo Flores d'Arcais, editor of the liberal Italian journal MicroMega. The paradox, he said, is that a conservative pope who struggled against modernity "acted like the C.E.O. of a company."
Rachel Donadio contributed reporting.
This article has been revised to reflect the following correction:
Correction: March 3, 2013
An earlier version of this article incorrectly stated that Eamon Duffy, a historian, is employed by Oxford University. He is a professor at the University of Cambridge.
