Democratic Republicans (Italy)
In 2005 the party sided with The Union and contested the 2006 general election within the lists of Antonio Di Pietro's Italy of Values (IdV). Consequently to this pact of federation, Ossorio was elected to the Chamber of Deputies in his home region Campania and sit in the IdV caucus.
On 20 September 2007, Ossorio announced that the Democratic Republicans were joining the centre-left Democratic Party (PD) alongside with fellow ex-PRI members of the European Republicans Movement (MRE). In 2010, however, the party returned into the PRI's fold.