Marcion donated 200,000 sesterces to the Church of Rome after Pope Hyginus died in 143, an impressive sum of money. The Church of Rome returned the money to Marcion after they learned of his odd doctrines (i.e. that the Old Covenant God was an evil demiurge). Many have conjectured that this "gift" was actually a calculated bribe on the part of Marcion and his adherents in order to obtain the bishopric of Rome.
At this same time, Tertullian (Adversus Valentinianos IV) claims that Valentinus was a candidate for bishopric of Rome. Needless to say, Valentinus and Marcion were passed over for Pope St. Pius I. Tertullian says after this great disappointment, Valentinus entered into schism and developed his advanced Gnostic doctrines. Marcion set up his parallel "church" at this time, as well.
Providentially, the Holy See was protected and Pope St. Pius I was chosen as the successor of St. Peter.