PSU sent three delegates to the congress of the Socialist International in 1980; Pier Paolo Gasperoni, Emilio della Balda and Dominique Morolli.[3] In the 1983 elections it won eight seats.
In the mid-1980s the party was renamed Unitary Socialist Party–Socialist Agreement. It won eight seats again in the 1988 elections, emerging as the third-largest party. It subsequently merged into the PSS.[1]