The party emerged in January 1994 as the successor to the Christian Democracy (DC), Italy's dominant party since World War II, following the final national council of the DC and the split of a right-wing faction led by Pier Ferdinando Casini, which had formed the Christian Democratic Centre (CCD).

In 1995, when his proposal to join the centre-right Pole of Freedoms coalition (composed of Forza Italia, National Alliance and the CCD) was rejected by the party's national council, Buttiglione, along with Roberto Formigoni, Gianfranco Rotondi and other bigwigs, formed the United Christian Democrats (CDU).

The PPI was represented in Romano Prodi's first government by three ministers: Beniamino Andreatta at Defence, Rosy Bindi at Health and Michele Pinto at Agriculture.

In 2002 DL was transformed into a full-fledged party, the PPI was merged into it and a cultural association named The Populars was formed.

Two members of the PPI and DL, Enrico Letta and Matteo Renzi, would successively serve as Prime Ministers in 2013–2016.