Leading his marchers down Rome’s Via Ostiense a few days ago, the rising star of Italian politics took a tumble. ‘F****** pothole! Who did this?’ roared Beppe Grillo, the foul-mouthed anarchic comedian who passes for the leader of the opposition in Italy these days.

On this occasion, the joke was on Grillo. As his opponents were quick to point out, Roman potholes — and I have seen some real shockers this week — are actually his responsibility.

It is now six months since his Eurosceptic, anti-capitalist, semi-bonkers party, the Five Star Movement, swept the board in mayoral elections across Italy. And Rome today is run by Five Star’s own mayor, Virginia Raggi, 37, a leading light in this madcap political movement whose slogan is ‘F*** Off’ — yes, really — and who still can’t fix a pothole.

It is now six months since his Eurosceptic, anti-capitalist, semi-bonkers party, the Five Star Movement, swept the board in mayoral elections across Italy

Yet Italian politics are no laughing matter right now. Indeed, if tomorrow’s referendum on constitutional reform goes the way Mr Grillo wants — and the way most people think it will — this country could be about to fall off a cliff.

The vote is on fiendishly complex plans by Italy’s shiny centre-Left Prime Minister Matteo Renzi — a 41-year-old latter-day Tony Blair — to cut the cost of the legislature and strengthen his government by reducing the power and size of Italy’s Senate (the upper house).

This would make it easier for him to pass legislation.

Renzi has staked his political reputation on a Yes vote. If he loses, he says, he’ll quit.

Plenty of experts think that a rejection of Renzi’s reforms will trigger a crisis which could eventually bring down the entire European project — the EU, the euro, the Brussels gravy train, Uncle Tom Juncker and all.

For a No vote could be the prelude to an Italian Brexit vote — Quitaly, Exitalia, Pasta La Vista, call it what you will. And if Italy leaves the EU, the EU is finished.

Certainly, it would bring on a general election at a time when Italy’s two popular anti-Establishment parties, Mr Grillo’s Left-leaning Five Star Movement and the country’s hard Right Northern League, are both committed to a popular vote on Italy leaving the euro and, thus, the European Union.

What’s more, the vote coincides with this week’s news that the number of migrants crossing the Mediterranean from Africa to Italy this year has reached a record 171,000.

Just when the Western liberal consensus thought 2016 could not get any worse, post-Brexit and post-Trumpquake, here comes a stonking great Italian meteorite.

This weekend also sees an Austrian presidential election which will return the most far-Right European head of state since Spanish dictator General Franco if Freedom Party candidate Norbert Hofer beats his Green opponent.

Beppe Grillo, the foul-mouthed anarchic comedian who passes for the leader of the opposition in Italy these days

Over the border in Germany, the hard-Right AFD recently overtook Chancellor Angela Merkel’s moderate CDU party in her own state. And France is only a few months away from a presidential election which will boil down to a choice between the extremist National Front and anyone-but-the-National Front.

In Italy, however, it is not just the far Right who are fiercely anti-immigration and avowedly Eurosceptic. Hostility to immigration and the EU can be found across the political spectrum, which makes the prospect of seismic political upheavals south of the Dolomites a distinct possibility.

On top of that, several Italian banks are in a critical condition. One of the country’s biggest institutions — the Banco dei Monti Paschi di Siena, the oldest bank in the world — is teetering on the edge of collapse.

Unless it finds an injection of five billion euros in the next few days, it will go under (seven other banks are believed to be in the same boat). A rescue package from gas-rich Qatar is said to be contingent on a Yes vote.

So before any diehard Brexiteers start cheering, it is worth remembering that an Italian banking collapse followed by economic catastrophe across the Eurozone could be extremely painful for Britain, too.

Some economists say the Italian story will be a much bigger version of the Greek crisis, but with one crucial difference — the country is too large to be rescued. The potential chaos, they argue, could make the 2008 financial crisis, following the collapse of Lehman Brothers, look like a quarrel over small change.

But millions of Italians still intend to vote No, arguing that these apocalyptic forecasts are exaggerated and things can’t get any worse.

No matter that the package of political reforms is so complicated that I have not met a single Italian who can recite the referendum question correctly.

(Say after me: ‘Do you approve the text of the Constitutional Law on “Provisions for exceeding the equal bicameralism, reducing the number of MPs, the containment of operating costs of the institutions, the suppression of the CNEL and the revision of Title V of Part II of the Constitution” approved by Parliament and published in the Official Gazette no 88 of 15 April 2016?’.)

The No campaign encompasses everyone from the far Left to the far Right and a great deal in between.

The vote is on plans by Italy’s centre-Left Prime Minister Matteo Renzi to cut the cost of the legislature and strengthen his government by reducing the power and size of Italy’s Senate

As well as Mr Grillo and his populists, the hard-Right Northern League want a No vote, too. So does former Prime Minister Silvio Berlusconi and his remodelled centre-Right Forza Italia party. Some members of Mr Renzi’s own party have come out for No.

The vote has united communists, fascists, Greens, trade unionists and big business. Even the staunchly Europhile Economist newspaper has just urged Italians to vote No, arguing that Renzi’s reforms are undemocratic and fail to address Italy’s deep seated problems.

This week, I have visited chic Italy, rural Italy and inner city ghetto Italy. And I have met everyone from wealthy bankers to Leftie students who will vote No.

When I ask if they fear instability and chaos, they just shrug and say: ‘This is Italy. What’s new?’ Talk of a wholesale collapse of the Italian economy, they say, is just ‘scaremongering’, like ‘Project Fear’ ahead of Britain’s Brexit vote.

Unlike Britain’s June referendum, though, there are few obvious fault lines. There are no clear north/south, Left/Right, old/young, metropolitan/provincial divides. The chief factor seems to be whether you rate PM Renzi and his attempts to reform one of the Western world’s most bloated political systems.

For Mr Renzi’s package of constitutional reforms — to speed up law-making and reduce the annual cost of the biggest legislature outside China by £430 million a year — should be a massive vote-winner.

Ask most people in Britain if they’d like to see fewer politicians and cheaper, more efficient government and you’d struggle to find anyone against.

A big problem for Mr Renzi, though, is that many Italians are deeply suspicious of any tinkering with the constitution, even if it is merely a recipe for inertia. This may be a system which has delivered 63 different governments since World War II.

This may be a system which has not produced an elected Prime Minister in seven years (Mr Renzi was not even an MP when the President plucked him from Florence’s city hall to run the country in 2014).

Two people, one wearing a mask of Italian Prime Minister Matteo Renzi (left), campaign for to vote 'Yes'

Italy is crying out for the financial stability and investment which the Yes camp is promising. But many Italians point out that these reforms give enormous parliamentary power to the party which comes out top. In this innately conservative society, many would rather have an impotent coalition than risk a dictator.

Newsagent Marco Gagliardi, 46, is not too worried that his No vote might cause a bank crash. That’s because his bank has lost all his life’s savings already.

He owns a busy tobacconist shop next to a superstore in the grand old Tuscan town of Arezzo. Like so many Italians, he’s saved all his life with the local bank, in his case the Banca Etruria. In 2014, he had 90,000 euros of both personal and company savings in an account that returned a miserly one per cent.

Then his local bank manager persuaded him ‘as a special customer’ to transfer to a much better rate in a supposed foolproof five-year ‘subordinate’ account. In fact, he had been lured in to buying bank bonds.

‘I didn’t know how it worked. I just trusted him and signed the form,’ says Marco.

A year later, he learnt that the government had ordered a ‘bail-in’ of his bank — meaning shares, bonds and larger deposits were being sacrificed to avert complete catastrophe.

More than 130,000 ordinary shareholders were hit. One pensioner in Civitavecchia lost £72,000 overnight and hanged himself.

The day after he learned the truth, Marco went to his local branch in a state of shock. The father-of-two shows me the bank statement of November 25, 2015. It reveals that his investment of 90,000 euros had suddenly been revalued at ‘796’.

As well as Mr Grillo (pictured) and his populists, the hard-Right Northern League want a No vote, too

One year on, he smokes like an old Alfa Romeo, has developed a twitch, cannot sleep and tries not to seethe all the time.

‘That bank failed because the bosses were handing out our money to their friends. In a normal country, they would now be in prison,’ he says, brandishing the fraudulent application form which the bank manager used to process his bond application.

The bank needed to prove that he was financially literate and had substantial assets. Neither applied in Marco’s case.

‘Look, they wrote on this form that I have “two properties”. I don’t even own my home. They said I had “a degree”. I don’t. They said I invested regularly “more than five times a year”. All untrue. They just showed me where to put my signature. Now they call me a speculator.’

He tries to be positive. ‘I’m young enough to come back and to fight this,’ he says. ‘But I know one poor man of 60 who has gone mad.’

I delicately ask about tomorrow’s referendum.

‘No! No! No! All the bank victims will vote No. We know Renzi and this government too well.’

He points out that the vice-chairman of the bank which ruined him is the father of Maria Elena Boschi, the glamorous young lawyer-turned-minister for constitutional reform who has drawn up the referendum. Little wonder they hate ‘the elites’ in these parts.

Up at the stunning town hall with its medieval frescoes, Arezzo’s mayor is a pro-European, independent moderniser from the political centre ground. A former university lecturer, Allessandro Ghinelli is a reformer who wants to slash the cost of basic services. But he turns out to be a No voter, too.

‘The constitution was created to unify Italy but Renzi is using it to divide the country. There are two types of politician. Those who work for Italy and those who work for themselves. Renzi is the latter.’

As night falls, I head for Florence and a Yes rally featuring two big-hitters, the Italian Home Secretary and the Mayor of Florence (the post previously held by Mr Renzi).

Mayor Dario Nardella is a smooth, multi-lingual chum of the Prime Minister and is under no illusions about the magnitude of this vote.

‘This referendum is as important as Brexit,’ he tells me. ‘It might be a different question but it is at the same level. The reputation of Italy in the world will go down if we vote No. The world will say: “Look, Italy doesn’t want to change.” And Europe and the financial markets will reflect that. The No vote offers no solutions at all, just negativity.’

Try as he might, it’s a pretty downcast gathering of just 100 Renzi supporters in a function room above a bustling food market. Half seem to have turned up for the free Prosecco and sandwiches. I do not sniff victory in the air.

Back in Rome, I meet the local co-ordinator for the hard-Right Northern League. Claudia Bellocchi, 46, a fast-talking Europhobe, believes that a victory for No tomorrow will kick-start the momentum towards an Italian Brexit.

‘My message to Europe? This will be another anti-establishment moment, like Trump’s victory. It will be a strong message for change. I just hope Italians will be as brave as Britain when the time comes to leave.’

In addition to the migration crisis, Claudia suggests that this year’s two big Italian earthquakes could be a factor in the No vote, too. Thousands are still waiting for temporary housing.

‘Renzi says the reforms will save 500 million euros,’ she says. ‘And yet he’s spent 2.5 billion euros on the migrants coming to this country. Most are not fleeing wars. They are 30-year-old men with phones, many of them delinquents. They get housing. But Italians displaced by these earthquakes have nowhere to live.’

So will there be an fresh earthquake right across Italy tomorrow night?

I expect a No vote. But I still think the most likely scenario is for Italy — a nation wearily familiar with shambolic political uncertainty — to muddle through somehow and stagger on to the next crisis.