Answer
Nicola Zingaretti resigned as the secretary of the Democratic Party (PD) in March 2021, leading to Letta's return. Zingaretti had been elected as the PD secretary in 2019, but his leadership had been criticized by some members of the party. He had also been unable to lead the party to victory in the 2020 regional elections. Letta had previously served as the PD secretary from 2009 to 2013.