Matteo Renzi urges Democrats to vote Sergio Matarella in as Italian president

Even if the first day of voting failed to produce a winner, there is now a strong possibility the Italian parliament will elect former Christian Democrat minister and constitutional court judge Sergio Matarella as the next president of Italy. Centre-left prime minister and Democratic Party (PD) leader Matteo Renzi hascalled on his party’s parliamentarians to vote for Mr Matarella in the name of “party unity”.

The crucial vote in this arcane election comes tomorrow morning. To be elected in the first three rounds, a candidate must win 673 votes, or two-thirds of the joint house electorate of 1,009 senators, deputies and regional representatives.

Given the improbability of obtaining that majority, Mr Renzi instructed his PD party to vote "scheda bianca" (no name) for the first three rounds. By the fourth round tomorrow morning, a simple 50-per-cent-plus-one majority of 505 is enough to secure success.

If Mr Renzi manages to have Mr Matarella (73) elected, he will have pulled off a daring move. Until now, many commentators had been convinced that Mr Renzi would only nominate a candidate who also had the “blessing” of his centre-right opposite number, media tycoon Sil vio Berlusconi.

Last night, though, Mr Berlusconi (78) made it clear his Forza Italia party would not vote for Mr Matarella, adding ominously: “It was Renzi who broke this agreement [on a presidential candidate], not us . . .”

By opting for Mr Matarella, the prime minister not only distances himself from Mr Berlusconi but he also strikes a blow for his own party’s unity. It remains to be seen if Mr Renzi can continue to govern without those Forza Italia votes which, twice in the last week, have proved critical in steering the ambitious Renzi reform programme through parliament.

In theory, at least, Mr Renzi should have the numbers to win tomorrow’s vote given that he can call on some 580 votes including not only his own PD party but also leftist SEL and centrist Civic Choice. That theory, though, does not allow for secret ballot “snipers” from the ranks of PD dissidents.

The last time the PD party conducted a presidential election, in May 2013, the ballot ended in bitter controversy as 101 “snipers”, mainly from within PD ranks, voted against the party candidate, former prime minister and European Commission president Romano Prodi. In the wake of that failed election, the PD party called on President Giorgio Napolitano to serve a second term of office, thus resolving a potentially destabilising situation.

Talking to The Irish Times in parliament yesterday, senior PD figures Anna Finochiaro and dissident Stefano Fassina were emphatic there would be no repetition of that "sniper" vote. Until now, the centre-left dissidents have argued, Mr Renzi had made a "Faustian" pact with Mr Berlusconi in return for Forza Italia's parliamentary support. What remains to be seen is just how Mr Berlusconi and Forza Italia will react. The media tycoon is not accustomed to the failure of his best-laid plans.

As it is, he now risks a backbench revolt from those who argue that continuing support for Mr Renzi in parliament has already alienated the party faithful. According to recent opinion polls, support for Mr Berlusconi’s party has more than halved since the 2013 general election, dropping from 29.18 per cent to 12-13 per cent.