Although some cardinals seem to have viewed him as papabile, a likely candidate to become pope, and may have received some votes in the 1958 conclave, Montini was not yet a cardinal, which made him an unlikely choice.[c] Angelo Roncalli was elected pope on 28 October 1958 and assumed the name John XXIII. On 17 November 1958, L'Osservatore Romano announced a consistory for the creation of new cardinals. Montini's name led the list. When the pope raised Montini to the cardinalate on 15 December 1958, he became Cardinal-Priest of Ss. Silvestro e Martino ai Monti. He appointed him simultaneously to several Vatican congregations which resulted in many visits by Montini to Rome in the coming years.
When did Montini finally become a cardinal?
15 December 1958