The United States is home to 10 of the 133 cardinals eligible to vote for the next pope. That's more than any other nation except Italy, home to 17 of the electors who will gather at the Vatican’s Sistine Chapel on Wednesday for the conclave that will choose a successor to Pope Francis.

Cardinals who will take part in the secret conclave to elect a new Catholic pope began checking into two Vatican hotels on Tuesday, where they will be barred from contact with the outside world as they decide who should succeed Pope Francis.

A papal conclave blends the political and the spiritual, cardinals and theologians say. Here, in Catholic belief, is how the Holy Spirit fits in.