Poppone cardinale di Brixen (odierna Bressanone) e del sud Tirolo fu eletto pontefice il 17 luglio del 1048. Il suo pontificato durò circa 22 giorni.
La sua elezione fu dovuta essenzialmente ai poteri tuscolani che sempre di più tendevano a Roma, soprattutto dopo la definitiva defenestrazione di Benedetto IX, contro tutte le direttive imperiali. L'enciclopedia cattolica così riporta la storia:
<<Benedict IX, who continued in his wonted manner to disgrace the papacy for a further period of eight months before disappearing entirely from history. On Christmas Day, 1047, an embassy sent by the Roman people brought the tidings of Clement's death to Henry III, at Pölthe in Saxony, and besought the emperor as Patricius of the Romans to appoint a worthy successor. The envoys, according to their instructions, suggested as a suitable candidate, Halinard, Archbishop of Lyons, who had a perfect command of the Italian tongue and was popular in Rome. Henry, however, in January, 1048, appointed Poppo, Bishop of Brixen, in Tyrol, and at once directed the Margrave Boniface to conduct the pope-designate to Rome.>>