By Crispian Balmer
ROME (Reuters) - Supporters of Italy's centre-left Democratic Party (PD) voted on Sunday to elect a new leader one year after the group lost power in a humbling defeat at a national, parliamentary election.
Previously led by former prime minister Matteo Renzi, the PD was thrown into turmoil by the 2018 ballot box beating as the electorate punished the party for not doing enough to tackle growing poverty, high unemployment and mass immigration.
Following months of internal feuding, three candidates have put themselves forward -- the governor of the Lazio region, Nicola Zingaretti, the interim PD chief Maurizio Martina and Roberto Giachetti, who is seen as the closest to Renzi.
Sunday's primary election is being held in some 7,000 voting booths set up around Italy by PD supporters.
Opinion polls suggest Zingaretti, whose actor-brother plays the lead role in the Italian TV police drama Inspector Montalbano, should win more than 50 percent of the vote.
If he fails to take an outright majority, party chiefs will gather on March 17 to decide the matter.
The primary vote comes at a time of growing tension within Italy's coalition government as the far-right League and anti-system 5-Star Movement struggle to overcome growing policy disputes in the face of an unexpected economic slowdown.
In a heartening sign for Italy's left, tens of thousands took to the streets of the financial capital Milan on Saturday to denounce racism and the anti-migrant policies of the League -- the largest such protest since the government took office.
The League has surged in the polls on the back of its anti-immigration stance, with a survey in Corriere della Sera daily at the weekend putting its support at 35.9 percent, more than double the 17.4 percent it won in last March's ballot.
By contrast support for 5-Star has dropped to 21.2 percent from 32.7 percent, as the group struggles to adjust from life as a vociferous, opposition force to a ruling government party.
Corriere put backing for the PD at 18.5 percent, little changed from a year ago but up from 16.1 percent that it registered in a similar survey at the start of February.
All three PD leadership contenders have ruled out cutting any coalition deals with 5-Star in future and say early elections would be needed if the current government fell.
Renzi, whose confrontational leadership style made him a highly divisive figure both inside and outside his party, has not openly backed any of the three candidates but has dismissed speculation that he might breakaway to create his own group.
"Whoever wins should not fear from me the guerrilla warfare that I suffered," he wrote in a Facebook post at the weekend, referring to the ferocious PD infighting that marked his time in charge and eventually led to a party schism.
(Reporting by Crispian Balmer; editing by David Evans)