Among those considered front-runners for the role are Cardinal Angelo Scola, archbishop of Milan; Canadian Cardinal Marc Ouellet, who heads the Vatican's office of bishops; Cardinal Leonardo Sandri, an Argentinian; and Cardinal Peter Turkson of Ghana.

Whoever gets the nod, the selection of a new pontiff is expected to go smoothly.

"We're not going to have a problem of two competing popes. If Pope Benedict still wanted to have influence, he wouldn't have stepped down," said senior Vatican communications adviser Greg Burke.

While not quite unprecedented, Benedict's resignation is certainly historic. The last pope to step down before his death was Gregory XII, who in 1415 quit to end a civil war within the church in which more than one man claimed to be pope.