Cardinal Pietro Pierleoni was born to the powerful Roman family of the Pierleoni, the son of the Consul Pier Leoni.

As a second son with ambitions, Pietro was destined for an ecclesiastical career.

He studied in Paris and entered the Benedictine Abbey of Cluny.

Later he went to Rome and occupied several important positions.

In 1130, Pope Honorius II lies dying and the cardinals decide that they willentrust the election to a commission of eight men, led by papal chancellor Haimeric, who has his candidate Cardinal Gregory Papareschi hastily elected as Pope Innocent II.

He is consecrated on February 14, the day after Honorius' death.

On the same day, the other cardinals announce that Innocent has not been canonically elected and choose, as Pope Anacletus II, Pierleoni, a Roman whose family members are the enemy of Haimeric's supporters, the Frangipani.

Anacletus' supporters are a mixture of anyone opposed to Haimeric, making him powerful enough to take control of Rome while Innocent is forced to flee North.

However, north of the Alps, Innocent gains the crucial support of St. Bernard of Clairvaux, Peter the Venerable, and other prominent reformers who personally help him to gain recognition from European rulers such as Emperor Lothar III, leaving Anacletus with few patrons.

Anacletus had been a relatively acceptable candidate for the Papacy, being well-respected, so rumors centering on his descent from a Jewish convert were spread to blacken his reputation.

Among Anacletus' supporters are duke William X of Aquitaine, who decides for Anacletus against the will of his own bishops, and the powerful Roger II of Sicily, whose title of "King of Sicily" Anacletus approves shortly after his accession.