He became a member of national importance of the Italian Socialist Party (Italian: Partito Socialista Italiano, or simply PSI) during the leadership of Bettino Craxi.

Formica was strongly critical of the PSI's transformation from a popular, social-based party into one involved in numerous corruption and official malfeasance scandals under Craxi.

He declared "the convent is poor, but the monks are rich" (in reference to PSI's financial problems, where its members were instead increasingly well endowed),[1] and defined PSI's national assembly as "a court of dwarves and ballerinas.

[2] Formica was one of the numerous PSI members involved in the Mani Pulite scandal of the early 1990s, although he was acquitted in the two trials raised against him.

[3] After Craxi's resignation as PSI national secretary in 1993, he supported Claudio Martelli as his successor.