After the death of Pope Pius on 9 October 1958, Tardini, though not a cardinal and not even a bishop, was prominently mentioned as a possible successor because of his familiarity with and closeness to Pius XII. Instead, Tardini was named Secretary of State by the newly elected Pope John XXIII, filling the previous vacancy. Having declined being made Cardinal by Pius XII in 1953, he accepted the red hat in the consistory of 15 December 1958 with the title of Cardinal-Deacon of "S. Apollinare alle Terme Neroniane-Alessandrine". He was ordained as a titular archbishop later that month.