After his election, Gregory XV had reformed the papal conclave system with his bull Aeterni Patris Filius of 1621, which was intended to streamline the conclave process, and this was the first papal election to follow these reforms.
Following the 1605 conclaves, papal elections had become standardized despite not being hereditary. The typical pope during the 200 years following Paul V's election that year was around seventy and had been a cardinal for a decade after a career as a canon lawyer. Popes typically came from the second-tier nobility of Rome or the Papal States.
The cardinals were primarily split in factions between those created by popes before Pope Paul V was elected in 1605, who numbered thirteen, those created by Paul, who numbered thirty-two, and those created by Gregory XV, who numbered nine. The two cardinals who had the most influence over the conclave were Scipione Borghese, the nephew of Paul V, and Ludovico Ludovisi, the nephew of Gregory XV. Ludovisi attempted to increase his influence over the conclave by becoming allies with the cardinals who originated from regions controlled by the Habsburgs.
Borghese had supported Pietro Campori in the previous conclave, which had elected Gregory XV, and Campori was his preferred candidate during this conclave as well. It was anticipated that Campori's age of 66 would be a benefit, because a Spanish memorandum had revealed that they viewed older cardinals as less likely to develop an independent foreign policy as pope. Because the French influence in this election was not expected to be much, Borghese anticipated that electing Campori pope would be easier, since French opposition had been the main thing preventing it in the previous conclave.