Italy's iconoclastic Five Star Movement may be on the brink of splitting: Can it be that the Grillini are toast?

The Grillini are partisans of comedian Beppe Grillo’s political movement, Five Star, the biggest single party in the Italian parliament. They came from nowhere to win a whopping 25.6 percent of the vote in February’s general elections and at the time seemed unstoppable.

Yet in recent local elections, which finished on June 9, Five Star's showing was so dismal that Italy's press is talking of the “flop Grillino.” Now they seem to be tearing themselves apart.

More worrying for the almost 8.8 million Italians who voted for the movement, are signs that it might already be on the brink of imploding. On June 11, Senator Adele Gambaro said the reason the movement only managed to win two of the 564 municipalities up for grabs in the recent local elections was Grillo himself.

“We are paying for the tone and communications of Beppe Grillo, his threatening blog posts, especially those attacking parliament," Gambaro said, referring to his disinterest in parliament. He recently described the legislature as “an empty can of tuna.”

Grillo leads the Five Star Movement, but chose not to enter parliament and now communicates mainly via his blog. In an angry response to Gambaro he wrote that she had made “false and harmful statements,” which had damaged him and the movement, commonly referred to as M5S. “I invite her to leave the M5S as swiftly as possible,” Grillo wrote.

Gambaro shot back. If M5S wanted her out, she said, they had better expel her, because she was going nowhere. So, now the movement is in crisis. Last week two deputies left Five Star and Bartolomeo Pepe, another senator, said it had become “too Grillo-dependent” and was destined for “self-destruction.”

Although the Five Star Movement attracted disenchanted voters from across the political spectrum, more came from the left of the political spectrum than the right. Many of them may have resolved not to vote for the movement again, after Grillo decided against forming a post-election coalition with the left-of-center Democratic Party, forcing it to ally with former Prime Minister Silvio Berlusconi's People of Liberty party. Three new nationwide opinion polls show that support for the Five Star Movement has fallen below 20 percent.

Speculation is rife that dozens of Five Star parliamentarians may leave the movement. Whether or not they do, M5S is clearly learning the hard way that being against something is easy, but being for something and taking responsibility for it is something else altogether. It is too early to say whether the Grillo balloon has burst, but it is certainly deflating.

(Tim Judah contributes to Bloomberg View's World View blog from Europe. Follow him on Twitter.)