Moreover, at 17 years old he was one of the founders of the anti-racist association "Black and not only" (Nero e non-solo), whose main aims were to promote liberal immigration politics and to create a multicultural and multiethnic society.

[16] During these years, he became a strong advocate of sustainable development and environmental protection; he also promoted many events against the Mafia and organized both the first "Antimafia Youth Camp" in San Vito Lo Capo and numerous initiatives in memory of Giovanni Falcone and Paolo Borsellino, the two anti-mafia magistrates who were assassinated in 1992.

In 1998, at thirty-three years old Zingaretti joined the Commission to draw up the socialist political platform for the new century, "Global Progress", chaired by Felipe González and composed, among others, by Martine Aubry, Shimon Peres and Ricardo Lagos.

He was also committed in promoting the peace process between Israel and Palestine, organizing many initiatives to support dialogue between young wings of the Israeli Labor Party and Fatah.

[19] From 1998 to 2000, he served as international relations spokesman for the Democrats of the Left (DS), the heirs of the PDS, and in 1998 he organized the Congress of European Socialists, in Milan.

In 1999 he took part in the Democrats of the Left delegation, along with Secretary Walter Veltroni, which visited Burma in support of the National League for Democracy and met the Nobel Peace Prize for 1991 Aung San Suu Kyi.

Zingaretti was among the protagonists of a season of important results for the centre-left and for the Democrats of the Left: in 2003, after eight years, the DS became again the largest party in the capital city, defeating the centre-right in the whole province of Rome.

[25] In 2010, Zingaretti refused to run as centre-left candidate in regional election and for this was heavily criticized by some members of his party, like the Mayor of Florence, Matteo Renzi.

[26] Few months later during the celebration of the 65th anniversary of the Liberation Day on 25 April 2010, Zingaretti participated together with the new president of Lazio Renata Polverini at an event organized in Rome at Porta San Paolo.

However, objects, slogans and insults were thrown toward the stage, contesting Polverini and her political background in the right-wing and Zingaretti was hit in the face by a lemon.

[28] Zingaretti's administration promoted the "ProvinciaWiFi" project, which consisted in the installation in squares, libraries and meeting places of the provincial territory, WiFi devices for free access to the Internet.

[34] However, on 24 September 2012, governor Renata Polverini, resigned after a controversy regarding the personal use of public money at the hand of some members of the coalition that supported her,[35] so on 4 October, Zingaretti retired his candidacy as Mayor, announcing his will to run as President of Lazio.

On 7 December 2012, Zingaretti resigned as President of the Province of Rome, putting an end to his administration 5 months before the natural deadline, to run in the 2013 regional election.

[42][43] He also promoted a new legislation on historic houses and natural parks and the regional law concerning the cultivation of cannabis for commercial, food and environmental purposes.

[47][48] On 4 March 2018, Zingaretti was narrowly re-elected president with 1,018,736 votes (32.9%), defeating the centre-right candidate Stefano Parisi (31.2%) and the Five Star's Roberta Lombardi (27%).

Despite the small margin of victory, Zingaretti's win was seen as a strong showing due to the poor electoral result of the centre-left coalition in the general election which was held on the same day.

[54][55] In August 2018, Zingaretti launched a political convention in support of his candidacy, named Piazza Grande ("Great Square"), which was held in Rome in October.

[60][61][62] On 1 December 2018, Zingaretti faced a motion of no confidence proposed by the centre-right coalition, which was rejected with votes 26 against and 22 in favor, with one no-vote from a Forza Italia member and three absents.

[63] On 3 March 2019, Zingaretti won the Democratic leadership election by a landslide, receiving 66% of the over 1.5 million votes cast and defeating Maurizio Martina and Roberto Giachetti.

[72] On 20 August, Conte resigned his post to President Mattarella and on the following day, the national direction of the PD officially opened to a cabinet with the Five Star Movement (M5S),[73] based on pro-Europeanism, green economy, sustainable development, fight against economic inequality and a new immigration policy.

[77] On 18 September, Renzi, who had been one of the earliest supporters of a M5S–PD pact in August,[78] left the PD and established a new centrist party named Italia Viva (IV).