ROME -- Pope Benedict XVI's surprise decision to resign on Monday immediately set off a flurry of speculation about his replacement, who will be called upon to guide the Roman Catholic Church through an increasingly secular era in which the church has lost the certainty it claimed for centuries.
Some Vatican observers predicted that the growing importance of the developing world to the church could weigh on the decision and, perhaps, lead to the choice of a non-European pope. But the voting bloc of cardinals coming from Europe remains sizable and influential, experts said.
"It's a premature question, though it's clear that two non-Italian popes in a row have broken the notion that the pope has to be Italian," said Alberto Melloni, a historian of the Roman Catholic Church and director of the John XXIII Center in Bologna, a liberal Catholic research institute. "But the church is not the Austro-Hungarian Empire where leaders alternate between countries. The pope is first of all bishop of Rome, and then the leader of the universal church."
Vatican experts argued that vision, rather than geography, would likely determine who would replace Benedict, and that the ability to communicate with a distracted world would be high on the list of desirable qualities. As nearly all of the cardinals eligible to vote were appointed by the current pope or his predecessor, John Paul II, it is likely that the next pope will share strong continuity in terms of vision and doctrine.
That said, bookmakers quickly issued the odds on the top contenders, with Cardinal Marc Ouellet of Canada, Cardinal Francis Arinze of Nigeria, and Cardinal Peter Appiah Turkson of Ghana among the early favorites. Cardinal Angelo Scola, the archbishop of Milan, was among the few Italians who was considered in the running by outsiders.
But there were those who noted that Pope Benedict appointed 67 of the 118 cardinals who will appoint his successor, and that 37 of them were from Europe, which remains the most substantial voting block and potentially the most influential.
"There's a very strong likelihood that it would be someone from Europe," said the Rev. Thomas J. Reese, senior fellow at the Woodstock Theological Center.
With the College of Cardinals in many ways reflecting the views of the pope and his predecessor, some Vatican experts suggested that the future pope would have similar theological positions, like Cardinal Ouellet and Cardinal Scola, as well as Cardinal Cristoph Schoborn of Vienna.
John Allen, a Vatican expert and biographer of Benedict XVI, said Cardinal Timothy Dolan, the archbishop of New York, could be a contender in a "multi-power" world in which America is no longer the one super power.
Acknowledgment of the growth of the importance of developing countries might also sway the choice.
In Brazil, the country with the world's largest Catholic population but one in which many feel distant from the Vatican, news of the pope's decision to step down came during the throes of the annual Carnival celebration.
"I see so many people who say they are Catholic and do not go to church," said Francisco Machado, 55, who was selling wigs and confetti to celebrants on a sidewalk in Rio de Janeiro. He described himself and his wife as practicing Catholics but said they were rare among their friends in actually regularly attending Mass.
Mr. Machado expressed skepticism over whether the next pope could come from Brazil. "We are not prepared to have a Brazilian pope, given the way the church is going," he said.
Andrew Chesnut, an expert on Latin American religions at Virginia Commonwealth University, said that the church faced big challenges in the region, even as Vatican leaders contemplate shifting demographics, with an estimated half of the world's Catholics now living in Latin America.
"The smart move for the Vatican for the future of the world church, which lies in the global south, would be a Latin American or African pope," Mr. Chesnut said. Still, he acknowledged that support for a European pope could pose an obstacle to such a choice if the Vatican focuses on the decline of the church in Europe.
Even if a Brazilian candidate or someone else from Latin America were chosen as pope, Silvia Fernandes, a sociologist at the Federal Rural University of Rio de Janeiro who specializes in Catholicism, said that big schisms within the church remained. She pointed to the rise of bishops in the Amazon who are focused on human rights, illegal deforestation and indigenous struggles, compared with the Catholic leadership in relatively prosperous southeastern Brazil, which she called more "institutional."
With more than 150 million Catholics and a rapidly growing population, Africa represents one of the church's best avenues for expansion. Church leaders have long been mindful of this, assiduously courting and promoting charismatic bishops and cardinals in nations with substantial Catholic populations, like Nigeria and Ghana.
In 2002, no less of an authority than Cardinal Joseph Ratzinger, who would eventually be chosen as John Paul II's successor, spoke of the merits of electing an African pope.
"For all its condemnation of racism, the Western world still has reservations about the third world," Cardinal Ratzinger said. "Yet, in Africa for example, we have truly great figures whom we can only admire. They are fully up to the job."
Speculation on a possible African pope was rife in 2005, when John Paul II died and one of his close aides, Cardinal Francis Arinze, a Nigerian, was touted as a possible successor. Mr. Arinze is now 80, and while he remains active he is not much younger than the current pope.
As a result, African hopes for the papacy have shifted to Cardinal Turkson of Ghana, a charismatic and popular senior church leader who is still in his mid-60s.
When Cardinal Turkson was asked in 2009 at a Vatican news conference about the possibility of a black pope, he replied: "An African pope? Why not?" according to the Catholic News Service.
After mentioning his fellow countryman Kofi Annan's tenure as United Nations secretary general, and Barack Obama's presidency, he added, "If by divine providence -- because the church belongs to God -- God would wish to see a black man as pope, then thanks be to God."
One looming question is the influence -- subtle or otherwise -- that the current pope will have on the outcome of the election.
The Vatican spokesman, the Rev. Federico Lombardi, said Monday that after his resignation on Feb. 28, the pope would retire from public view and would not participate in the appointment of his successor. But many wondered whether his presence would have an impact.
"The fact is that he's alive, and it's obvious that his opinion, his perception will be felt," said Paolo Rodari, a Vatican reporter for the daily Il Foglio newspaper. "Even if the pope will be discreet, those electing his successor are going to think about what Ratzinger would think of their choices."
Reporting was contributed by Lydia Polgreen from Johannesburg, Simon Romero and Taylor Barnes from Rio de Janeiro, and Elisabeth Malkin and Karla Zabludovsky from Mexico City.
This article originally appeared in The New York Times.