The party was founded as the Socialist Party of Italian Workers in 1947 by a splinter group of the Italian Socialist Party, due to the decision of the latter to join the Italian Communist Party in the Popular Democratic Front's electoral list for the 1948 general election. The split, led by Giuseppe Saragat and the sons of Giacomo Matteotti, took the name of Scissione di Palazzo Barberini, from the name of a palace in Rome where it took place. On 1 May 1951 it joined forces with the smaller Unitary Socialist Party and took the name Socialist Party – Italian Section of the Socialist International. On 7 January 1952 the PS–SIIS was ultimately renamed "Italian Democratic Socialist Party". From 1949 to 1965 members of the PSDI held the presidency of the Istituto Nazionale di Previdenza Sociale. In 1966 the party joined the PSI to form the Unified Socialist Party, but in 1969, after a dismaying result at the 1968 general election, it left the new unified party, taking the name Unitary Socialist Party. It returned to the PSDI name in 1971. In 1980 the party joined Christian Democracy, the Italian Socialist Party, the Italian Republican Party and the Italian Liberal Party in the five-party coalition which ruled the country until 1994. However the party's role in the coalition was minimal and was over-shadowed by the more powerful PSI. The PSDI was a member of Socialist International and a founder member of the Party of European Socialists. Its members of the European Parliament thus sat within the Socialist Group since 1979. In 1994 the party was expelled from the PES.
Decline and re-foundation
The PSDI was involved in the corruption scandals known as Tangentopoli and almost disappeared from the political scene. The 1994 general election resulted in an almost overnight decline of the Pentapartito coalition parties and the rise of Silvio Berlusconi-led Forza Italia, which absorbed many PSDI voters. In January 1995Gian Franco Schietroma was elected national secretary of the party replacing Enrico Ferri, who wanted to join the centre-right Pole of Freedoms. The followers of Ferri left and established the European Liberal Social Democracy and joined the centre-right Christian Democratic Centre. In 1998 the party, led by Schietroma, finally merged with the Italian Socialists, one of the successor parties of the PSI, to form the Italian Democratic Socialists. By then most members and voters of the party have joined other parties: Forza Italia, the Christian Democratic Centre and The Democrats. The party was re-established in 2004 with the same name, "Italian Democratic Socialist Party", as the continuation of the party of Saragat, so that the new PSDI numbers its congresses in perfect continuity with the late PSDI.
Popular support
The PSDI had its best result at its first appearance in the 1948 general election, when it gained 7.1% of the vote. In that occasion the party was successful in stealing many votes from the Italian Socialist Party, which was damaged by the split as well as by the alliance with the Italian Communist Party in the Popular Democratic Front. The PSDI found its heartlands in Northern Italy: 12.9% in the Province of Turin, 11.9% in Cuneo, 10.6% in Milan, 13.9% in Sondrio, 12.6% in Treviso, 15.9% in Belluno, and 14.9% in Udine. From 1953 to 1987 the party's support was around 4–5%, with the sole exception of 1963, when it gained 6.1%. In the 1992 general election, the last before Tangentopoli, the PSDI won just 2.7%. The party maintained for decades its strongholds in the North-West and North-East, but since the 1960s it started to gain support in Southern Italy. By 1987 the party's strongholds had moved South, especially Apulia, Campania, Basilicata, Calabria and Sicily, similarly to what also the other parties of Pentapartito were experiencing. This was partly due to the growth of regionalist parties in the North. After Tangentopoli, Mani pulite and subsequent political crisis, the PSDI has almost disappeared electorally, although it retains some support locally in the South, especially in Apulia. The electoral results of PSDI in general and European Parliament elections since 1948 are shown in the chart below.
