By Isla Binnie
ROME (Reuters) - Italian Prime Minister Matteo Renzi says "loads of people" will vote in a Dec. 4 referendum on his wideranging 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 organized crime in the south has contributed to a steady erosion of faith in politics.
"Voter abstention in the south favors '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 percent turned out in the regions south of Rome, compared with 66 percent 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 percent 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 percent 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 percent, 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.
Renzi's Democratic Party (PD) in Sicily is focusing on mobilizing its electorate and explaining the practical benefits of its plans, regional party secretary Fausto Raciti said.
"This is a reform that tries to imagine a country that moves at one speed, not at two different speeds, and we are pushing that idea," said Raciti.
His party is also pushing against the anti-system 5-Star Movement (M5S), which offers a protest vote against hardship which is seen as being aggravated by years of corruption. Some mainstream southern politicians have fueled the 5-Star fire.
Vincenzo De Luca, the outspoken PD president of Campania, Italy's third-largest region which surrounds the city of Naples, was recorded at a private meeting in mid-November apparently recommending influence peddling as a way to bring 'Yes' votes.
"Offer them a fish supper ... whatever the hell you have to do," De Luca said in the recording broadcast by Il Fatto Quotidiano newspaper. The veteran politician added that the region had received "rivers of money" from Renzi's government.
De Luca denied any wrongdoing and Interior Minister Angelino Alfano dismissed the incident, telling parliament that public spending was subject to strict rules.
Federico Benini, head of the Winpoll polling agency, said De Luca's words would resonate. "It is vital for the south to get money to restart its economy, and he played on that, on people's gut instincts."
(Additional reporting by Wladimiro Pantaleone in Palermo; Editing by Crispian Balmer)