After Brexit and Trump, it's Italy's referendum D-Day

Italian Prime Minister Matteo Renzi's future is on the line. Photo / AP

He burst on to Italy's political scene two years ago, promising to reshape his country's moribund politics, but it was an exhausted, careworn Matteo Renzi who urged Italians to say "yes" to his constitutional reforms when they vote in a referendum today.

"We have 48 decisive hours in which we can change the future of our children," the Prime Minister told crowds at a rally in his home town of Florence.

Six months ago, Renzi could not have foreseen this complicated piece of constitutional reform would turn out to be a defining, down-to-the wire battle for his political future.

But that was before Brexit and before Donald Trump.

Renzi, 41, has staked his personal future - and that of Italy and even Europe itself - on the reforms, which he says are vital to reinvigorating a nation mired in debt and ravaged by 36 per cent youth unemployment and a decade of stagnant middle-class incomes.

"If we want to shake things up in this country, it is now or never," he added, warning that it would be "decades" before Italians were given another chance at meaningful renewal.

Analysts warn that as a prominent centrist voice in Europe, Renzi's departure will weaken the EU and potentially trigger a fresh banking crisis if uncertainty caused by a "no" vote derails plans to recapitalise Italy's debt-laden banks.

Renzi promises that his reforms will liberate Italy from its near-permanent state of legislative gridlock, but his detractors in the populist Five Star Movement say they will only further entrench the corrupt establishment classes.

"We are a country that is stuck in the mud," Beppe Gillo, the stand-up comedian who founded the Five Star Movement told a crowd of several thousand in Turin at his own rally, urging his supporters to vote with their guts and send Renzi packing.

"The country is split," Grillo added. "It's a situation of mental stasis ... You have to react here," he said, pounding his stomach with his fists.

Elements of Renzi's own Democratic Party are opposing the reforms, as is the anti-immigrant Northern League and Silvio Berlusconi, the former Prime Minister, who claimed they could pave the way for "dictatorship".

With public polls banned since November 18, the outcome of a bad-tempered campaign remains difficult to predict.

The last available polls showed "no" up to 10 points ahead, but "yes" campaign officials say privately that their own polls show the contest narrowing.

The "yes" camp is pinning their hopes for a surprise victory on a late boost from 1.6 million expatriate votes that are believed to favour Renzi and what they call a "silent majority" of Italians who they believe will vote for political stability.