The national elections last month produced no clear winner, but President Giorgio Napolitano said the 61-year-old Bersani was best positioned to create a government given "the most difficult circumstances" -- a reference that the political leader has a comfortable majority in the lower house, but that the Senate is split.
Bersani's forces finished first, but he has ruled out a coalition with former Premier Silvio Berlusconi's conservative alliance, which would risk further alienating the voting base of Bersani's Democratic Party.
But if he shuns Berlusconi, Bersani will need to win support from Parliament's new third bloc, a populist, anti-euro movement founded by comic-turned-political leader Beppe Grillo. Grillo has rejected a vote of confidence to support any established party -- and support in the required vote of confidence for a new government to go forward.
Still, some Grillo lawmakers broke ranks over the weekend and voted to support Bersani's candidate as Senate speaker, a move that infuriated Grillo.
Bersani pledged dialogue with political forces in the coming days, seeking a balance between "a government seeking the change expected by the Italians and one able to carry out reforms."
Outgoing Premier Mario Monti's centrist forces finished fourth with around 10 per cent of the vote.Italian elections were held February 24-25, but Napolitano could not consult with leaders until after the new Parliament was seated last week and caucus leaders were chosen.