[1][2] As mentor and closest advisor of PD's former secretary Nicola Zingaretti, Bettini is considered one of the most influential and powerful politician within the party.

During the 1970s, he joined in the Italian Communist Youth Federation (FGCI), where he met Walter Veltroni, to whom he will always be very close.

He retained his two posts after the Bolognina turning point and the consequent birth of the Democratic Party of the Left (PDS).

In 1993, he was the strategist of Francesco Rutelli's candidacy for mayor of Rome, who was elected in the second round in December, defeating the right-wing candidate, Gianfranco Fini.

Since 2019, when Nicola Zingaretti was elected secretary of the PD, Bettini became one of the most influential politicians within the party, as well as his closest advisor.