DemoS was formed in July 2014, following the split of the left-wing faction from the Populars for Italy (PpI). The party, led by Lorenzo Dellai, Andrea Olivero, Mario Marazziti, Mario Giro and Lucio Romano, re-affirmed the strategic (not just tactical) alliance with Matteo Renzi's Democratic Party (PD), while the PpI considered it temporary and wanted to restructure the centre-right camp instead. At its start, the party counted eight deputies, two senators, one deputy minister and one undersecretary.[6][7][8][9]
In November 2014, the "For Italy" group in the Chamber welcomed the two deputies of the Democratic Centre (CD).[10] In December, the two senators of DemoS, Olivero and Romano, left the "For Italy" group, which was later disbanded, to join For the Autonomies, a miscellaneous group composed of minor autonomist and/or centre-left parties.[11] In September a ninth deputy, Maurizio Baradello, joined the party and the parliamentary group;[12][13] Baradello would die in May 2017.[14]
In early 2015, Demos adopted a new symbol,[15] Dellai was elected president of the party and Paolo Ciani coordinator.
In January 2016, the "For Italy" group changed its name to "Solidary Democracy – Democratic Centre",[10] following a strengthening of the alliance with CD.[16] In February, Giro, formerly an undersecretary, became deputy minister of Foreign Affairs; Giro was thus one of the party's two deputy ministers, along with Olivero at Agriculture.[17]
In the 2018 general election, CP obtained a mere 0.5% and no seats; thus, DemoS was excluded from Parliament. Moreover, Dellai was defeated in a single-seat constituency in Trentino.[23] However, in the simultaneous 2018 regional election in Lazio, Ciani was elected regional councillor, at the head of a regional list named "Solidary Centre".[24]
In May 2022, the party held its first national congress.[34] Ciani, until then coordinator, was elected secretary, while Giro was re-elected president.[35]
In the 2022 general election, party leader Ciani was elected to the Chamber for the PD.
In the 2024 European Parliament election, the party ran with the PD and supported three candidates: Bartolo, Covassi and Marco Tarquinio.[36] Despite the first two being incumbents, the only elect was the latter.