What is the precedent for a pope to resign?TR: The number of popes who may have resigned has been estimated as high as 10, but the historical evidence is limited. Most recently, during the Council of Constance in the 15th century, Pope Gregory XII resigned to bring about the end of the Western Schis

Could a pope resign? Would a retired pope still be infallible? If a pope resigns and another is elected, are there in effect two popes?