A strong supporter of Romano Prodi, in 1995 he founded, with him, the Olive Tree coalition, and on 30 November 1999 he won a by-election to replace him in the Italian Chamber of Deputies.

He then became president of the Federal Assembly of the new Daisy party, and was re-elected to the Chamber in the 2001 general election.

[2] After being re-elected Deputy in the 2006 general election,[3] he was appointed Minister of Defence in the cabinet of Prime Minister Romano Prodi, a position he retained until 2008 when the governing Union coalition crumbled and new elections were called.

Parisi, Enrico Morando and Stefano Ceccanti presented a motion asking for the immediate calling of primary elections open to all members of the party.

Parisi ran for the post against former deputy secretary Dario Franceschini but obtained 92 votes out of 1,258.