[3] After attending the classical high school in nearby Sant'Angelo dei Lombardi with excellent grades, he won a scholarship in the Augustinianum College and enrolled at the Catholic University of the Sacred Heart in Milan, where he graduated in law and then started working as a consultant at Enrico Mattei's Eni legal office.

[6] De Mita was appointed deputy secretary of the Christian Democracy in 1969, serving under the leadership of Arnaldo Forlani; he hold the position until February 1973.

Craxi had always promoted his reformist drive as opposed to the inaction of the Christian democrats and in 1987 he clashed with De Mita for the breaking of the so-called "relay pact" (patto della staffetta), under which the Italian Socialist Party (PSI) would have had to cede the leadership of the government to the DC in the last year of the legislature.

[9][10][11] In 1984 De Mita pushed the future president of Italy, Sergio Mattarella, and Leoluca Orlando to intensify their political commitment with the task of cleaning up the Sicilian branch of the DC from Mafia control.

[9] After the elections of 1987, De Mita waited a year to become Prime Minister and was appointed on 13 April 1988, heading a five-way coalition (Pentapartito) with DC, PSI, PSDI, PRI and PLI.

[9][13] Three days later, on 16 April 1988, in Forlì, Red Brigades killed Senator Roberto Ruffilli, an advisor of De Mita.

[16][17] In June 1988 his cabinet approved the relocation of 72 U.S. Air Force F-16 fighters to Italy, in response to Spain's request to remove them from its territory.

[6][9][22] In September 1992, he was appointed Chairman of the Bilateral Commission for Constitutional Reform, a position he left in March 1993 when was succeeded by Nilde Iotti.