By Isla Binnie
ROME (Reuters) - Former Italian prime minister Matteo Renzi looks set to trigger a leadership contest at a meeting of his ruling Democratic Party (PD) on Monday which could delay the early election he has been pushing for since he was toppled as premier last year.
Rising tensions in the PD have deflated Renzi's bid for an vote by June, around a year ahead of schedule, with a sizeable minority threatening to split and take away a chunk of votes.
When the riven party meets in Rome, Renzi is expected to play a disruptive card by stepping down from the helm, sparking a leadership bid which could imply months of campaigning.
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"We are used to surprises, but if nothing changes overnight the leadership contest will probably start, meaning the party secretary resigns," Michele Emiliano, the PD governor of the southern Puglia region, told state TV RAI.
Emiliano is among critics who say Renzi has taken the party too far to the right, and want to challenge him before any vote.
Both Emiliano and former PD lower house floor leader Roberto Speranza would almost certainly run in a leadership race which now looks inevitable, a minister close to Renzi told Reuters.
Another obstacle to an early vote are the current electoral laws which ultimate arbiter President Sergio Mattarella has said need to be aligned between both houses of parliament.
"Right now, it seems more likely that we will have elections in 2018," the minister said. Renzi's supporters are convinced he would win a leadership congress or primaries.
"Our own polls show that Renzi can beat anyone who might stand against him," the minister said.
Main opposition parties, including the 5-Star Movement which polls within a whisker of the PD, want an early vote.
A notable exception is former premier Silvio Berlusconi's Forza Italia party, which trails the anti-immigrant Northern League on Italy's fractured right wing. Berlusconi told La Repubblica newspaper on Sunday "taking the country to the ballot boxes in these conditions would be irresponsible".
Polls show no party would win an outright majority under the current proportional system, probably dooming Italy to another of the unwieldy coalitions long blamed for instability.
PD veterans including former prime minister Massimo D'Alema warn against toppling current Prime Minister Paolo Gentiloni, widely seen as Renzi's proxy, without first changing the law.
Underlining how much a popular vote against his proposed constitutional reform has weakened Renzi's position, 40 PD senators issued an appeal last week to keep Gentiloni in place.
Only 32 percent of PD voters want elections to be held in June, while 58 percent would want to wait until the end of the legislature in 2018, according to a Winpoll survey for the Huffington Post published on Sunday.
Speranza, who has been a thorn in Renzi's side since he resigned as floor leader in 2015, told La Repubblica: "We need to work to build an alternative point of view to Renzi."
(Additional reporting by Crispian Balmer; Editing by Stephen Powell and David Evans)