Italy's ruling centre-left Democratic Party (PD) is set to hold leadership primaries on 30 April, party officials announced on Friday.
Ex-premier Matteo Renzi is being challenged by justice Minister Andrea Orlando, Puglia Governor Michele Emiliano and Carlotta Salerno, a local politician from Turin.
Orlando and Emiliano are Renzi critics, while Salerno positions herself as an independent who says she would focus on Italy's regions, the outskirts of its cities and the political grassroots if elected
Renzi triggered the primaries by standing down as PD secretary last Sunday, to seek a new, stronger mandate in early primaries.
His supporters were said to have been pushing for the leadership primaries to be held earlier, on 9 April while the other candidates wanted more time.
After the primaries the new leader will officially take over at a national assembly on May 7, according to PD officials.
Renzi stood down as prime minister in December after a crushing defeat in a referendum on constitutional reforms he claimed would streamline Italy's political machinery.
The former premier is eager to return to power and is pushing for national elections to be held this year rather than early 2018 as scheduled.
A group of leftist rebels including former PD leader Pier Luigi Bersani broke away from the party earlier this week. A small but vociferous minority, they have long criticised Renzi's shifting of the party towards the political centre and his allegedly autocratic treatment of dissenters.
