ROME (Reuters) - Italy’s anti-establishment 5-Star Movement, potentially just months away from winning power, is wrestling with a problem it thought it would never have to deal with: choosing a leader.

5-Stars movement Luigi Di Maio (C) looks on as he arrives for a news conference in Rome, Italy, October 17, 2016. REUTERS/Max Rossi/Files Photo

And it is proving difficult.

A maverick among Europe’s band of new political parties, 5-Star has no formal hierarchy, believing instead in a horizontal structure where its supporters participate directly in decision-making through online ballots.

The movement founded seven years ago, which bases its appeal on fighting corruption and cronyism, is running neck-and-neck with former Prime Minister Matteo Renzi’s Democratic Party (PD) in opinion polls.

It was the big winner in a Dec. 4 referendum in which Italians rejected Renzi’s constitutional reforms, forcing him from office and leading to calls from most political parties for elections in the first half of 2017, a year ahead of schedule.

But forming a government would mean nominating a prime minister, and rivalries are building among likely contenders that could hamper the movement’s election hopes or destabilize a future 5-Star government.

Party sources say a battle for support is already in progress between telegenic 30-year-old Luigi Di Maio, until recently the favorite, and Roberto Fico, 42, a former communications expert who has taken a swipe at his rival by urging the party to resist the cult of political celebrity.

A third contender has also recently emerged who may yet eclipse them both: Alessandro Di Battista, a 38-year-old deputy from Rome who shows far more passion than his rivals in decrying the corruption endemic in the mainstream parties.

5-Star is leading in some opinion polls, despite squabbles and scandals that have plagued the party’s mayor of Rome, Virginia Raggi. But a leadership battle is a new and risky challenge to its fragile unity.

“This is a movement with no real structure and as the stakes get higher so will personal ambitions and infighting,” said Francesco Galietti at political risk consultancy Policy Sonar.

Before the next election 5-Star’s 135,000 members will choose their prime ministerial candidate in an online vote. The date of the vote, the regulations and the candidates have not yet been fixed. So far only Di Maio has confirmed he will run.

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Italy’s mainstream parties are trying to rewrite the electoral rules to keep 5-Star from power but they have no guarantee of success against a party that could emerge with the biggest share of votes.

LIMELIGHT

Di Maio was groomed as 5-Star’s prime ministerial candidate by the movement’s founders: comedian Beppe Grillo and internet guru Gianroberto Casaleggio, who died this year.

Grillo, 68, 5-Star’s spiritual head and de facto leader, has ruled out running for office, and in any case he would be barred under the movement’s internal rules due to a conviction for manslaughter over a 1981 road accident. Yet he could remain a major influence over a 5-Star government.

Soft-spoken, moderate and immaculately turned out in suit and tie, Di Maio was at first seen as the perfect foil to Grillo’s outbursts and theatrical rants.

But he did little to hide his ambition. As his public profile has risen, so has the disapproval of fellow 5-Star parliamentarians who accuse him of hogging the limelight.

When he gave an interview to Vanity Fair in May, full of personal details that included his sex life with his girlfriend, he drew a rare public rebuke from his fellow deputy Fico.

Some of Di Maio’s colleagues also accuse him of withholding information and siding too closely with Rome mayor Raggi, who is disliked by a faction of the party’s lawmakers.

Di Battista, often unshaven and casually dressed, is the new idol of 5-Star’s supporters. His popularity shot up after he spent the summer touring the whole of Italy on a scooter to campaign against Renzi’s constitutional reforms.

The bearded Fico represents 5-Star orthodoxy. He reminds his colleagues, none of who had real political experience when they entered parliament in 2013, not to forget their roots or be tempted by celebrity status.

“It’s so easy to find you are changing bit by bit without even realizing it is happening,” he told Reuters.

Fico says if it were up to him, 5-Star would not even pick a candidate for prime minister but decide everything collegially.

“People are obsessed with leaders, as though one person can have the answers to everything, but then they fail one after the other,” he says. “Politics has become like X-Factor.”