The president has the final say in naming the prime minister and is often called on to resolve political crises in the euro zone’s third largest economy.
Italy's lawmakers have failed to elect a new head of state for a third day, with no consensus candidate emerging to replace outgoing President Sergio Mattarella.
On Wednesday, many of the 1,009 lawmakers and regional delegates cast blank ballots as they had in the previous two voting rounds, a way of playing for time while their leaders negotiate.
A fourth round of voting, which begins at 1000 GMT on Thursday, may prove less predictable because the threshold required for election is considerably lower.
Prime Minister Mario Draghi remains in the frame but worries that his promotion to president might cause his coalition government to disintegrate and trigger an early parliamentary election have clouded his prospects.
"We would have weeks of confusion if Draghi were to leave the government," said rightist League leader Matteo Salvini on Wednesday.
"It would be a problem amid a health crisis, an energy crisis, an economic crisis," he added.
Of the main party chiefs the only one who is publicly supporting Draghi's candidacy for president is Enrico Letta of the centre-left Democratic Party (PD).
The president is a key figure in Italy.
He has the final say in naming the prime minister and is often called on to resolve political crises in the euro zone's third largest economy, where governments on average survive barely a year.
A successful candidate needs a two-thirds majority in any of the first three rounds. From the fourth round the threshold is lowered to an absolute majority, or 505 votes.
This means it is possible that one side could try to push through a candidate hoping that, in the secret ballot, they can win support from unaffiliated lawmakers or some votes from the other side.
Such a move is considered more likely to come from the centre-right, which has slightly more lawmakers.
Francesco Boccia, a senior PD figure, told the conservative bloc on Wednesday that if it forced through one of its own as president, the multi-party coalition backing Draghi's government would collapse.
"If the majority splits (over the presidential vote), as far as we are concerned the legislature is over, it's a statement of fact," Boccia said in a radio interview.