Some minor parties and associations, including The Italian Socialists of Bobo Craxi, Socialism is Freedom of Rino Formica and the Association for the Rose in the Fist of Lanfranco Turci, immediately welcomed Boselli's proposal, while in June 2007 the New Italian Socialist Party (NPSI) divided in two groups: the first, led by Stefano Caldoro and Lucio Barani, opted to join The People of Freedom and retained the NPSI identity; the second, led by Mauro Del Bue and Gianni De Michelis, agreed to join the Socialist Constituent Assembly.

Despite this, the national council of the PS chose to continue the experience of SL to build a "secular, libertarian and left-wing" force.

[29] The PS was renamed Italian Socialist Party (PSI), chose to support joint candidates with the PD and to run its own lists in the forthcoming regional elections,[30] opening the way to Craxi's return.

[25] In December 2010, Boselli, long-time SDI leader and PSI founder, who had left active politics after his 2008 defeat, joined the Alliance for Italy (ApI), led by Francesco Rutelli.

[28] In November 2011, Carlo Vizzini, a senator of The People of Freedom (PdL) and former leader of the PSDI, joined the party, giving it parliamentary representation after more than three years.

Common Good coalition headed by PD leader Pier Luigi Bersani,[35] whom the PSI had supported in the centre-left primary election.

The party obtained 4 deputies and 2 senators, including Nencini, from the lists of the PD and right after supported Enrico Letta's government.

During the third party congress in November 2013, Nencini was re-elected secretary, beating Franco Bartolomei of the "frontist" left and Angelo Sollazzo of the "autonomist" wing.

[43][44] Contextually, Carmelo Lo Monte, elected in 2013 with the Democratic Centre, joined the PSI's sub-group and the party as a full member.

In Città di Castello, the Socialist mayor Luciano Bacchetta was re-elected in the first round and the party obtained 21.5% of the vote.

In the 2017 local elections, the party obtained its best results in Nocera Inferiore (13.2%),[59] Palmi (12.0%),[60] Galatina (9.5%),[61] Narni (8.6%)[62] and Trapani (8.8%)[63] while losing ground in its historical stronghold of Carrara (6.5%),[64] where a Socialist was the incumbent term-limited mayor.

In September 2017, Michela Marzano, originally elected with the PD, joined the PSI sub-group in the Chamber as an independent[65] while Lo Monte left in November.

[5] In July 2022, the party announced it would join the Democratic and Progressive Italy list led by Enrico Letta, within the centre-left coalition, for the 2022 general election.

In the 2010 regional elections, the party confirmed its strength in its strongholds: 4.2% in Umbria, 3.7% in Calabria, 4.6% in Basilicata, 9.7% in Apulia (along with SEL) and 3.5% in Campania.