There were three main parties in the Sacred College, with cardinal-nephews of the deceased Popes as leaders:[2] Three cardinals of the Italian ruling families (d'Este, Medici and Sforza) were not counted among the members of these factions.

Although Campori had two significant opponents (Republic of Venice and Cardinal Orsini), Borghese was sure that he would be able to achieve his election on the first day of voting, by acclamation.

[2] Finally, the leaders of factions agreed to elect aged and ill Cardinal Alessandro Ludovisi of Bologna, who seemed to have been the ideal candidate for a temporary pontificate.

Pope Gregory XV in his Bull Aeterni Patris Filius (November 15, 1621) prescribed that in the future only three modes of papal election were to be allowed: scrutiny, compromise, and quasi-inspiration.

The rules and ceremonies prescribed by Gregory XV were kept substantially the same until Pope John Paul II issued the constitution "Universi Dominici Gregis" in 1996.