Is it possible for someone to be an antipope even though the majority of cardinals claim he is pope? The case of Antipope Anacletus II proves that it is possible for a majority of cardinals to claim a man is pope while he, in reality, is an antipope. In 1130, a majority of cardinals voted for Cardinal Peter Pierleone to be pope. He called himself Anacletus II. He was proclaimed pope and ruled Rome for eight years by vote and consent of a absolute majority of the cardinals despite the fact he was a antipope. In 1130, just prior to the election of antipope Anacletus, a small minority of cardinals elected the real pope: Pope Innocent II. How is this possible? St. Bernard said "the 'sanior pars' (the wiser portion)... declared in favor of Innocent II. By this he probably meant a majority of the cardinal-bishops." (St. Bernard of Clairvaux by Leon Christiani, Page 72) Again, how is this possible when the absolute majority of cardinals voted for A...


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"Should any infraction whatsoever of this norm occur and be discovered, those responsible should know that they will be subject to grave penalties according to the judgment of the future Pope".
And Pope Benedict reiterated this in this context in the Acta Apostolicae Sedis (1 March 2013). After the conclave and the Mass, when the legitimate Pope receives his Munus and consequently his ministry to exercise it, the Cardinals will be obliged to take a vow of obedience to the elected Supreme Pontiff.
So think of the legitimate Cardinals who have remained negligent in the face of 10 years gone by with this new pontificate that is approaching.
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https://www.vatican.va/archive/aas/documents/2013/marzo2013.pdf