 Pope Innocent II named Baldwin a cardinal-priest of Santa Maria in Trastevere no later than in 1137, when he appears for the first time in this dignity.Later that year, he was in the Mezzogiorno, probably in the trail of the Emperor Lothair II.According to Peter the Deacon, he and a son of Pier Leoni ("filium Petri Leonis") were at Montecassino to pacify a revolt when, in July, he participated in a debate over the rule of Cassinese monasticism in the presence of the emperor.