Analysis: Italy's Grillo facing showdown as 5-Star mutiny swells ROME (Reuters) - Beppe Grillo, the fiery comic whose populist 5-Star Movement stunned Italy by winning a quarter of the votes in February's election, is facing his biggest test since the vote with rebellion brewing among his novice lawmakers. Publicly blamed by one of his own senators for the party's poor showing in local elections earlier this week, in which it won only two towns out of more than 500, Grillo faces the threat of a mutiny that could blow the party apart. Though there is no clear sign of any organized revolt within the anti-establishment movement, as many as 30 parliamentarians are said to be ready to quit the party for various reasons. Some have balked at being asked to hand back daily parliamentary allowances as part of the movement's rejection of political privilege. Others chafe at Grillo's deep intolerance of dissent in a grassroots movement where everyone is supposed to have a say. A vote next Monday on whether to expel dissident senator Adele Gamabaro, who said the leader's bullying style was to blame for the local election debacle, could test whether the 5-Star Movement can survive or will fade away like a host of other short-lived protest parties. What has emerged is his limits as a leader. Any politician knows that managing things in such an absolutist, authoritarian manner is impossible," said Leonardo Morlino, a professor of political science at LUISS university in Rome. Grillo's success was built in equal measure on his own charisma and skill in articulating boiling frustration at a discredited elite, and on widespread public hopes for a new way of doing politics built on youthful energy and the power of the Internet. Few campaigners could match his drive and showbusiness flair as he toured up and down Italy in a camper van before the election, drawing tens of thousands to town square rallies where he blasted a corrupt and bloated elite. His popular blog attracts thousands of comments from young people sick of being shut out of decisions and turned off by a television system divided between Silvio Berlusconi's Mediaset empire and state broadcasting carved up between the main political parties. "This conception of participatory democracy with a leader like Grillo is perhaps the single biggest contradiction in the 5-Star Movement and it's what's coming out now," Morlino said. How it plays out is still completely open. Grillo is an intelligent person and he may understand what's happening and adapt. But he may not. Few predict the 5-Star Movement will disappear as long as Italy remains stuck with the corruption, unemployment and political stalemate that fuel its protests, but opinion polls show its support has slipped steadily since the election. The latest survey by the SWG polling institute put it on 17.9 percent, down two points from a week earlier and in third place behind the centre-left Democratic Party (PD) and Berlusconi's People of Freedom (PDL) party. Theories about why the movement has hit trouble mostly trace the problem back to Grillo's refusal to accept an accord with the centre-left after the February election, which left no party with a majority of its own in parliament. His fixed belief that the PD was no different from the PDL ended up handing a share of power to Berlusconi, to the dismay of many supporters for whom the media billionaire and former prime minister is the incarnation of all that is wrong with the system. "The 5-Star Movement is full of contradictions," said Roberto D'Alimonte, one of Italy's best known political analysts. It chose not to go into government and enact some of its policies when it could have. It said it wanted to get rid of Berlusconi and it had a chance to do it - and it didn't. Two lawmakers have already walked out protesting against Grillo's domineering style, though other party members say disputes over allowances were the real cause. A third was thrown out for defying orders not to take part in TV talk shows. With growing talk that the movement risks fragmenting in dissent and recrimination, Grillo urged supporters on Thursday to make their voice heard, saying the explosion of rage that had led to the triumph in February appeared to have weakened. "I have only one voice and it's grown hoarse after hundreds of meetings," he wrote on his blog this week. "The media, the mouthpiece of the System, has attacked the Movement with unheard-of violence," he said. Make your voice heard or Italy will be lost. But the weeks of wrangling have worn away at disillusioned supporters. "I can't take these discussions any more, parliamentarians saying anything they like, Beppe threatening to smash everything, arguments between ultra-loyalists and provocateurs," wrote Sandro Campanelli, a commentator on Grillo's blog. We're making a shameful spectacle of ourselves. Additional reporting by Steve Scherer Editing by Barry Moody and Andrew Heavens