Italy's Prime Minister Matteo Renzi gestures as he attends television talk show "Porta a Porta" (Door to Door) in Rome, Italy, November 30, 2016. Photo: Reuters/Remo Casilli

Italian Prime Minister Matteo Renzi says “loads of people” will vote in a December 4 referendum on his wide-ranging constitutional reform, but he may be privately hoping that those in the poorer south stay at home.

Renzi has pledged to resign if Italians reject his plan to shrink the upper house Senate, effectively turning a debate on highfalutin points of law into a personal vote of confidence.

Before a blackout was imposed on opinion polls two weeks ago, all surveys showed the No camp was well ahead, sending shivers through financial markets wary of instability in the euro zone’s third-largest economy.

The polls said the strongest anti-reform sentiment appeared to be in the southern regions, which are home to more than a third of the electorate, but which also register the lowest turnout figures in Italy – a fact which might help Renzi.

Economic stagnation and widespread organised crime in the south has contributed to a steady erosion of faith in politics.

“Voter abstention in the south favours Yes, because they are more inclined to vote No, but they are also less likely to vote,” said Carlo Buttaroni, president of pollsters Tecne.

The last time Italy held political elections, for the European parliament in 2014, 51.7% turned out in the regions south of Rome, compared with 66% in the north-west, which includes the financial capital Milan.

Disaffection is deepest in Sicily and Sardinia, whose economies have been hit harder by years of recession. Just 42.7% of islanders cast a ballot in 2014.

In a further twist, turnout is traditionally much lower in referendums. This is because normally at least 50% of the electorate have to vote for the plebiscite to be valid. So one tactic to register disapproval is simply to stay at home.

This happened in Italy’s last referendum in June on oil drilling rights, when turnout was just 31.2%, guaranteeing that the measure failed. However, under Italian law, votes on changing the constitution have no set quorum.

“We are worried that people opposed to this reform will simply not vote, thinking that is all they have to do, like in June,” said an official with the Northern League party, which is campaigning hard against Renzi’s overhaul.