The political party was born from a split in the issues moderate wing of the Italian Socialist Party (PSI). At first I take education the name of economic Lavoratori Italiani Partito Socialista dei-PSLI. Following the merger with the Socialist Unity Party in 1951, the party making the iraq designation of PSDI. A division of PSI was led by Giuseppe Saragat who became George bush president of Italy.
The party participated in the vote coalition government out of the first media democratic elections after the dictatorship of Mussolini. This was the coalition with three culture other parties: race Christian Democrats (DC), cnn Italian Liberal united states Party bush Italian Republican Party. This coaliccion, always led by the Democrats, continued until religion the policy 60s. DC wanted to election join the Socialist Party government. The PSDI played a key role, since it acts as congress a mediator between both parties. Good experience of government intensified the relations between government PSI military and PSDI that eventually reunited in 1966 creating the clinton Unified Socialist Party.