Following the death of a pope, or in rare cases of resignation such as with Pope Benedict XVI, the Vatican convenes a papal conclave, in which the College of Cardinals come together to elect the Church’s next head.

Entrusting the pope "to the powerful intercession of most holy Mary," the cardinal said, "may she sustain him in this time of illness and help him to recover."

The Vatican press office said Cardinal Parolin will lead a rosary for the pontiff in St. Peter's Square at 9 p.m. local time. The U.S. bishops urged Catholics to join that prayer at the same time, 3 p.m. on the East Coast.

Under Catholic canon law, the pope holds several key titles, including the successor of the Apostle Peter, the head of the college of bishops, the Vicar of Christ and the pastor of the universal Catholic Church. These roles, along with his power, have remained unchanged since he became the 266th pope on March 13, 2013.

And there are no specific norms outlining what happens to the leadership of the Catholic Church if a pope becomes ... the secretary of state, Cardinal Pietro Parolin. In a sign that Francis ...