Luigi Di Maio is so confident his populist Five Star Movement (M5S) will triumph in today’s Italian elections that he has already presented his would-be cabinet.

In what he called an “act of transparency”, the impeccably groomed 31-year-old politician named his dream team, which includes an economist, a criminologist, a doctor and an Olympic gold medallist, three days before the election.

Brushing off rivals who ridiculed the move, he boasted: “We will be the ones laughing on Monday, when Italians will probably take us to 40%.”

Voting began in Italy on Sunday morning and polls will close at 11pm.

M5S will almost certainly emerge as the biggest single party, but with final opinion polls putting it on roughly 28% (and some pollsters suggesting it might secure an even higher vote), it is unlikely to reach the 40% required for a majority and to govern alone. To steer into power it would have to flout a rule sacred to its origins and form a coalition, a scenario already rejected by the party’s founder, the irreverent comedian Beppe Grillo, and those devoted to its anti-establishment principles.

But however things pan out, pundits are starting to wonder whether the elections will make or break a party whose phenomenal growth since its inception in 2009 has been boosted by mounting public anger and distrust of the political elite.

In Naples and other poor parts of the south, more voters are backing Di Maio, a local boy. Photograph: Alamy Stock Photo

“It probably is a ‘now or never’ moment,” said Mattia Diletti, a political scientist at Sapienza University, Rome. “They will perform strongly, but if they have to rule with another party I’m pretty sure there will be tension within the movement.”

Di Maio, who is as cryptic as the party he represents, played a shrewd game by announcing his ministerial line-up early. Apart from capturing media attention, it allowed him to counter claims that M5S officials are incompetent and at the same time appease ardent supporters with an “anti-politician” list.

He is convinced that the party can replicate its electoral success of 2013, when it won more than 25% of the vote, almost 10 points higher than polls had predicted, and became Italy’s second-largest party.

The eldest of three siblings, Di Maio was born in Avellino, a town in the southern Campania region. His CV may be modest – he has worked in restaurants, on building sites and as a steward at Napoli football club – but at the age of 26 he became the youngest ever deputy speaker of Italy’s lower house of parliament.

Described as the reassuring face of a party built by a rabble of rebels, he was elected as its candidate for prime minister in September in a move aimed at attracting moderate voters. The strategy is paying off: M5S has maintained its strength in the polls even though its squeaky-clean image has been tarnished by corruption scandals during the campaign.

There is a lot of support for M5S here; they represent something different

Support is particularly prominent in Di Maio’s Campania, where swaths of voters are counting on the man who they affectionately call “Gigi” being the master of a sweeping change, long awaited in an area of Italy ravaged by poverty and organised crime.

“I haven’t voted for 40 years but this time I will vote for M5S,” said Alessandro Esposito, 64, from Naples. “They are young and fresh and have good ideas. We should give them a chance.” At Braceria, a modern pizzeria in Avellino, a waiter spoke enthusiastically about Di Maio, who pops in whenever he’s in town. “He is always very kind and cordial,” Maurizio Florio said. “There is a lot of support for M5S here; they represent something different.”

It is easy to understand the appeal. At one of his final rallies, in a packed theatre in Caserta, about an hour’s drive from Avellino, Di Maio spoke about providing a universal income for the poverty-stricken; making it easier for young Italians to start a family; cutting business taxes; investing in education and repealing what he called “useless” laws.

Southern voters say the Five Star leaders may have younger, fresher ideas. Photograph: Alamy Stock Photo

“I want citizens to wake up each day and feel the difference in their lives,” he said, “not only to hear politicians saying that ‘everything is OK’.”

M5S has excelled in using the internet to track voter sentiment, a tactic that has often led it to oscillate between one stance and another, prompting suspicion among those who are less convinced. But forming a coalition, as Di Maio has suggested the party should do, should it fail to reach a majority, might be a step too far for grassroots supporters.

A peculiar feature of the Italian political system allows parties to cast aside previous loyalties and form partnerships with others after a vote. With this in mind, commentators have mooted the far-right League (formerly Northern League), now in an alliance with Brothers of Italy and Silvio Berlusconi’s Forza Italia, as a potential partner for M5S. Described as the “nightmare scenario”, this proposal has so far been ruled out by leaders of both parties, but with M5S and the League more closely aligned on issues such as immigration, it is not beyond the realms of possibility.

With a hung parliament widely predicted, however, the more likely outcome of the vote will be a “grand coalition” between Forza Italia and the centre-left Democratic party.

So where would that leave M5S?

“If they stay out of the game, there will be some turmoil and it will be difficult for Di Maio to keep the party united,” said Jacopo Iacoboni, a journalist at La Stampa and author of The Experiment, a book about the Five Star Movement. “A part of M5S will revert to its origins.”

Given Di Maio’s popularity with supporters, the party’s golden rule – that MPs should serve two terms only – might also be put to the test. Unless the rule is changed, this run will give Di Maio his final mandate. Although it is unlikely that he will be allowed to step down so easily, the party’s future could hinge on another popular M5S official: Alessandro Di Battista.

“If Di Maio doesn’t gain power then there is another card to spare,” said Iacoboni. “Di Battista is Plan B; he has only done one mandate so he is perfectly in the running.”

With M5S and the League more closely aligned on issues such as immigration, could they become partners?

FIVE STAR AGENDA

Wages

A minimum monthly income of €780.

Laws

Repeal 400 “useless” laws, including labour and pension reforms, to allow earlier retirement and make firing harder.

Migrants

Di Maio wants an end to the “sea taxi service” to rescue migrants.

Environment

Fossil fuels to be phased out by 2050.

