Italy's 87-year-old President Giorgio Napolitano was set to be elected by parliament for an unprecedented second mandate on Saturday after the main political forces pleaded with him to stand, but a new protest party denounced a "coup d'etat".
The ex-communist is considered as being above the party political fray and is respected by both the left and the right, which have been at loggerheads since a general election in February that yielded no clear winner and left the economy in limbo.
Beppe Grillo, leader of the Five Star Movement protest party which won a quarter of the vote and is shaking up Italy's political world, said Napolitano's candidacy was a sign of how "desperate" traditional parties had become.
He called for a massive open-ended protest in front of parliament later on Saturday in a blog post, saying: "I will stay all the time that is necessary. We have to be millions... Either we have some democracy or we die as a country."
Grillo's party is supporting Stefano Rodota, a well-liked 79-year-old academic and human rights advocate, for president but he has failed to get elected in five rounds of voting since Thursday.
Napolitano would be the first Italian president to be elected for a second seven-year term and as recently as last week he had ruled out the prospect of staying on, saying he had "done everything I could" to end the stalemate.
He is not expected to serve out the full mandate but instead only stay in office the time needed to end the deadlock and then resign at the end of a political career that began in the Second World War when he was an anti-fascist activist.
"I must assume my responsibilities before the nation," Napolitano said in a statement on Saturday ahead of a sixth round of voting by lawmakers, calling on parties too to show "collective responsibility" for the country.
Political leaders including the left's Pier Luigi Bersani and the right's Silvio Berlusconi, as well as outgoing Prime Minister Mario Monti, held separate talks earlier on Saturday with Napolitano.
They said it was "necessary and urgent that parliament show unity and national cohesion with the re-election of President Napolitano," the presidency said in a statement after the talks.
Monti's party Civic Choice said the outgoing premier, whose cabinet has limped on with only interim powers, had "pleaded" with Napolitano to stay "in the higher interest of the country".
A former top Italian Communist Party official, Napolitano was credited with engineering former European commissioner Monti's rise to power after then premier Berlusconi's chaotic ouster in 2011 during a wave of panic on the financial markets.
Trying to find a solution to the current political crisis has proved too much, however, also because Napolitano currently does not have the power to dissolve parliament and call early elections -- a threat that could help push for a compromise.
If re-elected Napolitano would regain that power.
Italian presidents, who hold a mostly ceremonial role that takes on huge importance during times of instability, cannot call elections in the last six months of their mandate under the constitution.
The centre-left, which narrowly won elections in February but failed to get enough votes for a majority in parliament, has been in total disarray.
The leadership of the leftist Democratic Party (PD) -- its secretary Bersani and chairwoman Rosy Bindi -- resigned on Friday after two presidential candidates it proposed failed to get elected.
Ex-trade union leader Franco Marini and widely respected former European Commission chief Romano Prodi have both now withdrawn their candidacies.
Prodi lost on Friday after 101 lawmakers from the centre-left rebelled against their leadership and did not vote for him -- a sign of deep divisions.
"Collective Suicide", read the headline of an editorial in leftist daily Il Fatto Quotidiano, adding that the PD was "in tatters".
"The epicentre of the crisis is the Democratic Party," La Repubblica said, accusing rebels from the centre-left of "blind cannibalism" and blaming the "mediocrity of the party leadership".
Bersani had been the target of growing criticism after he threw away a big lead in the opinion polls ahead of the February elections.
The eurozone's third largest economy has been in political deadlock since then with politicians unable to strike a compromise to form a government in the middle of a steep recession.