Italy's Democratic Party (PD) formed an alliance with a smaller centrist group on Tuesday in a move seen as boosting the centre-left's chances of preventing a right-wing triumph in an election next month.
The ballot is set for Sept. 25 and polls show a conservative alliance is on course for victory, with the far-right Brothers of Italy set to be the largest single party.
Italy's election law favours parties that form broad alliances.
The PD, the largest party on the centre-left, has agreed to team up with the Azione party in an effort to make up ground on the rival alliance.
PD leader Enrico Letta told a news conference that the alliance made the election an open race and said the PD was open to drawing in other groups in Italy's fragmented political landscape.
"We believe that it is unthinkable that our country, after the government of (Prime Minister Mario) Draghi, will be led by a rightist government," Letta said.
The conservative alliance led by Giorgia Meloni's Brothers of Italy includes the rightist League and the more moderate Forza Italia party of former prime minister Silvio Berlusconi. It is currently polling at around 45%, while the PD and Azione are close to 30% together.
DRAGHI'S LINE
Azione and its existing +Europa ally poll only around 5-7% in surveys, but two senior members of Berlusconi's Forza Italia defected to Azione last week, saying Italy's conservative bloc had become too extremist.
The PD and Azione pledged to stick to the foreign policy of Prime Minister Draghi in support of Ukraine and to meet targets required to access billions of euros in funding from the European Union.
"The elections will be a choice between an Italy that is one of the great countries of Europe and an Italy allied with (Hungarian Prime Minister Viktor) Orban and (Russian President Vladimir) Putin," Azione leader Carlo Calenda said.
Berlusconi and League leader Matteo Salvini have been very close to Putin in the past and Italian newspapers last week reported that both their parties have had contacts with the Russian embassy in recent weeks despite the war in Ukraine.
Berlusconi has denied talking to the Russian ambassador while the League has denied any wrongdoing.
(Reporting by Angelo Amante; Writing by Keith Weir; Editing by Agnieszka Flak and Andrew Heavens)