VATICAN CITY - Cardinals from around the globe locked themselves inside the Sistine Chapel on Tuesday to choose a new leader for the world's 1.2 billion Catholics and their troubled church, surrounded by Michelangelo's imposing frescos imagining the beginning and the end of the world.
The 115 scarlet-robed men entered their conclave with a final appeal for unity to heal the divisions that have been exposed by Pope Benedict XVI's shocking resignation and revelations of corruption in the Vatican bureaucracy.
Led by prelates holding a crucifix and candles, the cardinals chanted the Litany of Saints, the hypnotic Gregorian chant imploring the intercession of the saints, as they filed into the chapel and took their oath of secrecy.
Outside in St. Peter's Square, onlookers began to cast their eyes toward the 6-foot chimney on the roof.
Assuming the cardinals vote today - and there's no guarantee they will - the first puffs of smoke could emerge from the chapel chimney by 8 p.m. (3 p.m. EDT) — black for no pope, white if a pope has been chosen.
With a dramatic closing of the thick double doors and the exhortation "Extra omnes" or "all out," the ritual-filled conclave began beneath Michelangelo's frescoed "Creation" and before his "Last Judgment" — potent images for the task at hand.
Benedict XVI's resignation has thrown the church into turmoil and exposed deep divisions among cardinals grappling with the apparently conflicting needs for a manager to clean up the Vatican's dysfunctional bureaucracy and a pastor who can inspire Catholics at a time of waning faith and growing secularism.
The buzz swirled around Cardinal Angelo Scola, an Italian seen as favored by cardinals hoping to shake up the powerful Vatican bureaucracy, and Brazilian Cardinal Odilo Scherer, a favorite of Vatican-based insiders intent on preserving the status quo. Other names included Canadian Cardinal Marc Ouellet, who heads the Vatican's powerful office for bishops, and U.S. Cardinal Timothy Dolan, the exuberant archbishop of New York.
In a final appeal before the conclave began, the dean of the College of Cardinals, retired Cardinal Angelo Sodano, appealed for unity within the church, urging the cardinal electors to put their differences aside for the good of the church.
"Each of us is therefore called to cooperate with the Successor of Peter, the visible foundation of such an ecclesial unity," Sodano said. He said the job of pope is to be merciful, charitable and "tirelessly promote justice and peace."
He was interrupted by applause from the pews — not so much from the cardinals — when he referred to the "beloved and venerated" Benedict XVI and his "brilliant" pontificate.
Sitting in the front row was Benedict's longtime aide, Archbishop Georg Gaenswein, who reported that Benedict was watching the proceedings from the papal residence in Castel Gandolfo, according to a Vatican spokesman the Rev. Thomas Rosica.
For over a week, the cardinals have met behind closed doors to try to figure out who among them has the stuff to be pope and what his priorities should be. But they ended the debate on Monday with questions still unanswered, and many cardinals predicting a drawn-out election that will further expose the church's divisions. The conclave proceeds in silence, with no debate.
During the discussions, Vatican-based cardinals defended their administration against complaints that they have been indifferent to the needs of cardinals in the field. At one point on Monday, the Brazilian head of one Vatican office reportedly drew applause for challenging the Vatican No. 2, who has been blamed for most of the bureaucracy's administrative failings.
"Let us pray for the cardinals who are to elect the Roman pontiff," read one of the prayers during the Mass. "May the Lord fill them with his Holy Spirit with understanding and good counsel, wisdom and discernment."
A few hundred people braved thunderstorms and pouring rain to watch the Mass on giant TV screens in St. Peter's Square. A handful knelt in prayer, eyes clenched and hands clasped. They stayed on through the rain, watching the narrow chimney atop the chapel for the first puffs of smoke.
In his final radio address before being sequestered, Dolan on Tuesday said a certain calm had taken hold over him, as if "this gentle Roman rain is a sign of the grace of the Holy Spirit coming upon us."
He said he at least felt more settled about the task at hand. "And there's a sense of resignation and conformity with God's plan. It's magnificent," he said during his regular radio show on SiriusXM's Catholic Channel.
Some of the faithful outside alluded to the huge challenge facing the next pontiff.
"It's a moment of crisis for the church, so we have to show support of the new pope," said Veronica Herrera, a real estate agent from Mexico who traveled to Rome for the conclave with her husband and daughter.
Yet the mood was not entirely somber.
A group of women who say they are priests launched pink smoke from a balcony