ROME (Reuters) - "O-ne-sta ! O-ne-sta! O-ne-sta!"
When Virginia Raggi, the anti-establishment 5-Star Movement's candidate for Rome mayor, arrived at a modest pizzeria in the city for a fund-raising event, her supporters greeted her with a rhythmic call for honesty - her movement's battle-cry.
The anti-graft message sums up the identity and appeal of a grass-roots party that may soon run not only Rome but Italy.
Opinion polls suggest Raggi, a 37-year-old lawyer, is likely to win the June 5 election and become the Eternal City's first woman mayor.
That could provide a launch-pad to national government for a movement that is unique among Europe's raft of anti-establishment parties which have drawn strength from public anger over high unemployment and immigration.
Unlike the leftist Syriza in Greece and Podemos in Spain, or the far-right National Front in France and Austria's Freedom Party, 5-Star is an idelogy-free party with voters from the left and right alike.
Despite many setbacks since it was founded seven years ago, 5-Star has swelled to become Italy's second largest political force and is just a whisker behind Prime Minister Matteo Renzi's centre-left Democratic Party.
If opinion polls are correct, it could become the first "anti-system" government in a major European country at national elections which are due in 2018 but widely expected next year.
Victory in Rome is a vital stepping stone. If Raggi runs the city well it would blunt Renzi's charge that 5-Star may be good at protesting but is too inexperienced to govern. If she fails, the blow to the party's momentum would be enormous.
"5-Star is not going to go away whatever happens, but I can't deny that winning Rome is fundamental for us," says Carla Ruocco, a lower house deputy and one of 5-Star's five member national leadership.
Raggi, a city councillor who was chosen as candidate for mayor in an on-line ballot of 5-Star's members, says she is focused just now on solutions to the capital's problems rather than the party's future.
Rome's previous rulers treated it as a "feud", she says, offering jobs in city companies and tenders for useless building projects in exchange for votes, while services from transport to trash collection were "devastated" by mismanagement and neglect.
"They attack me because they are afraid that I can break this mechanism, that Rome can become a normal city, don't you find that terrible?," she told Reuters.
5-Star is seeking income support for the poor, tax cuts for small businesses and state run banks to fund investments in new technologies, renewable energy and high-quality agriculture.
It promises to slash politicians' pay and privileges, and hold a referendum on whether Italy should remain in the euro.
Such proposals resonate with its main voter base among the young, the relatively well-educated and those in the poor south. But its chief asset remains its image as the only party that is serious about taking on graft and privilege.
"There is corruption at all levels," said Federico Tucci, a 50-year-old building engineer who works with both the public and private sector and, like the other 200 guests, paid 20 euros for his pizza at the fund-raiser to help Raggi's campaign.
"To work well you always need a favour from someone, and those who want to do things properly are demoralised," he said.
Italy slipped two places to 61st in Transparency International's 2015 corruption perceptions index, second to last among the 28 European Union countries above only Bulgaria.
That, along with listless economic and job growth, helps explain why Renzi's popularity has slid for the last year. Many graft scandals have involved his own Democratic Party.
5-Star has its problems too. Its politicians are novices and several have run into trouble, especially at the local level. It suspended the mayor of Parma, the largest city it controls, after he disclosed he was being investigated over the way he appointed the head of the local opera house.
This lines up potential clashes between the Rome city hall and national government if Raggi wins.
The capital is saddled with over 12 billion euros (9.21 billion pounds) of debt, partly towards the Treasury. Raggi says she will renegotiate the terms of payment. It remains to be seen whether Renzi will cooperate.
She also opposes Renzi's bid for Rome to host the 2024 Olympics, saying the city has far more urgent priorities.
Raggi said she did not want to believe speculation the premier would try to block her efforts if she wins. "If Renzi is honest he will behave honestly towards Rome," she said.
Editing by Richard Balmforth