A trade union leader in the Italian Confederation of Christian Workers, in 1922–1923 he served in the first government of Benito Mussolini as Under-secretary for Industry and Commerce.

In order to avoid having to become a member of the Fascist Party, he also resigned his position as a schoolteacher, and earned his living as a successful businessman, first as a salesman and then as an industrialist.

In 1943–1944 he was a co-founder of the new Christian-Democratic party (DC), and became a leader of its left-wing faction,[2] together with men like Giorgio La Pira, Giuseppe Dossetti and Enrico Mattei (the future boss of ENI, the Italian government-owned petrochemical giant).

However the extreme right-wing of the party – led by Giuseppe Pella, Guido Gonella, Salvatore Scoca and Giulio Andreotti – joined hands with the trade-unionist left – led by Giovanni Pastore, Giorgio Bo and Achille Marazza – in an "uprising" against the party leadership, in order to get Giovanni Gronchi ("Parliament's man") elected instead.

It was marked by the ambition to bring about a gradual "opening to the left", whereby the Socialists and the Communist Party would be brought back into the national government, and Italy would abandon NATO, becoming a non-aligned country.

In an attempt to escape the deadlock, in 1959 Gronchi appointed as prime minister a trusted member of his own Catholic left-wing faction, Fernando Tambroni, sending him to Parliament with a "President’s government" but no pre-arranged majority.

In 1960 there were bad riots in several towns in Italy, particularly at Genoa, Licata and Reggio Emilia, where the police opened fire on demonstrators, killing five people.

An "opening to the left" of sorts happened soon after his mandate was over; the first centre-left coalition was formed by Aldo Moro as soon as 1964, when the Socialists (but not the Communists) entered the government.

A 2000 Parliament Commission report concluded that the strategy and operations by the clandestine, US-supported, "stay-behind" Gladio was designed to "stop the PCI, and to a certain degree also the PSI [Italian Socialist Party], from achieving executive power in the country".