FILE PHOTO: 5-Stars movement Luigi Di Maio looks on as he arrives for a news conference in Rome, Italy, October 17, 2016. REUTERS/Max Rossi/File Photo

ROME (Reuters) - Members of Italy’s anti-establishment 5-Star Movement, which leads most opinion polls before a national election early next year, began voting on Thursday to elect their leader and candidate for prime minister.

Barring a colossal surprise the winner will be Luigi Di Maio, the 31-year-old lower house deputy who has been groomed as leader over the last few years by Beppe Grillo, the comedian who founded 5-Star as a protest movement in 2009.

The party’s supporters are voting online on a dedicated platform linked to Grillo’s blog, reflecting 5-Star’s credo of internet-based direct democracy.

Voting will end at 7 p.m. (1700 GMT) on Thursday, but the result will not be known until Saturday, when it is announced at 5-Star’s annual three-day gathering in the Adriatic coastal town of Rimini.

There are eight candidates, but Di Maio’s victory is considered a formality. He is one of Italy’s most prominent and popular politicians and his seven rivals, mostly local councillors, are virtually unknown even to 5-Star supporters.

The only people seen as having any chance against him decided not to run, opening the party up to accusations of failing to run a proper contest.

Roberto Saviano, author of the best-selling novel Gomorra, said on Facebook that he wanted to run for the post “to help 5-Star out of a pathetic situation”. Saviano is not a party member and so is not eligible.

Probably the only risk for Di Maio would be if voting were distorted by another hacking attack against 5-Star’s internet platform. In August an anonymous hacker revealed he had broken into the system to obtain secret data on 5-Star’s members and donors.