By Gavin Jones and Steve Scherer
ROME (Reuters) - In the sound and fury of Italy's election campaign, the man who will pick the next prime minister never says a word.
President Sergio Mattarella, known for his reserved personality and dislike of controversy, hails from the now-defunct Christian Democrat party, which mastered the art of political compromise for 50 years after World War Two.
Soft-spoken and devoutly Roman Catholic, Mattarella normally performs a ceremonial role, delivering speeches in which he extols universal values such as tolerance, the family and national unity.
Yet after parliamentary elections on March 4, his job becomes more political. If the result is inconclusive, as opinion polls suggest, it is the president's task to pick a prime minister who must then win the support of the new parliament.
If no one achieves a working majority, the 76-year-old Sicilian must cajole political rivals into putting campaign rancor behind them and find common ground, just as his predecessor did five years ago after the last general election ended in deadlock.
"Mattarella will have a tough job after the election, but he is very well equipped for it. He has all the Christian Democrat skills to come up with some kind of arrangement," said Roberto D'Alimonte, politics professor at Rome's Luiss university.
Mattarella comes from a family of Christian Democrats. His father served as minister several times in the 1950s and '60s, and his brother was shot dead by the mafia in 1980 while governor of Sicily. His own political career began after his brother's murder and spans more than three decades.
He held a number of ministerial posts in the 1980s and 90s, also serving under Giulio Andreotti, one of the wiliest figures in post-war Italian politics. He became president in 2015 after serving as a constitutional court judge.
After the election, there will be some time for negotiations before pressure builds. Parliament will meet for the first time on March 23, allowing at least three weeks of talks before a government can be seated.
After the country came close to default during the euro zone debt crisis seven years ago, investors may get uneasy should Italy, which is saddled with the bloc's second highest public debt, be left rudderless for too long.
If Mattarella were unable to broker a political deal, he would be forced to call fresh elections. However, sources close to the president say he is highly reluctant to trigger a repeat vote which might be no more conclusive than the first.
Polls suggest the conservative coalition made up of former prime minister Silvio Berlusconi's Forza Italia (Go Italy!) and its far-right allies will win the most parliamentary seats, but probably will fall short of an outright majority.
In that case, Mattarella could ask a center-right figure to try to form a government, or he could turn to Luigi Di Maio, leader of the anti-establishment 5-Star Movement, which looks set to become Italy's largest party.
Or he may do neither, opting instead for a non-partisan technocrat who is more acceptable to a broad range of parties.
Italy has had several of those, from central bankers Carlo Azeglio Ciampi and Lamberto Dini in the 1990s, to former European Commissioner Mario Monti, appointed at the peak of the euro zone debt crisis in 2011.
Michele Ainis, a public law professor and constitutional expert, said if the election yields no obvious majority, then Mattarella can pick anyone he wants to be prime minister, as long as the candidate can win a parliamentary confidence vote.
"It could be a second-choice figure that no one is even mentioning now," Ainis said.
Parliament's first task will be to elect the speakers of the two houses. That process, which may happen before a prime minister has been found, could provide a hint as to which majority can be formed, Ainis said.
Reading the poker-faced Mattarella's intentions is far harder than it was for his predecessor.
Giorgio Napolitano, president from 2006 to 2015, had a declared political agenda and made no secret of his antipathy to 5-Star. Mattarella, on the other hand, steers clear of any overtly political pronouncements.
The 5-Star rejected an alliance with the center-left Democratic Party (PD) after the 2013 vote, prompting the formation of a right-left coalition government. Now it says it is willing to discuss a policy platform with the other parties if there is a hung parliament, though it rules out horse trading over ministries.
Before a poll blackout came into force on Saturday, 5-Star was polling at around 28 percent, ahead of the ruling PD on 23 percent and Forza Italia on 16 percent.
Francesco Galietti, head of political risk consultancy Policy Sonar, said despite the animosity between 5-Star and its mainstream rivals, Mattarella may try to aim for a broad coalition that does not exclude the largest party.
Galietti reworked a quotation from plain-speaking U.S. President Lyndon Johnson to describe Mattarella's possible attitude to 5-Star.
"With more than half the electorate not voting or voting for anti-establishment parties, the president might decide he wants to have an elephant inside the tent pissing out, rather than an elephant outside the tent pissing in," he said.
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(additional reporting by Massimiliano Di Giorgio; editing by David Stamp)