Former Prime Minister Romano Prodi failed to win election as Italy's new president on Friday after his nomination by the center-left bloc enraged Silvio Berlusconi and increased the chances of a snap election in the summer.
Berlusconi's center-right boycotted the vote for Prodi, one of the media magnate's oldest political foes, and protested outside parliament, accusing center-left boss Pier Luigi Bersani of breaking a promise to put forward a candidate it could accept.
The vote was the fourth in a complex election process by 1,007 electors from both houses of parliament and regional representatives. A fifth and sixth vote are expected on Saturday.
center-left officials said they would continue with Prodi as their candidate on Saturday but the failure of four votes so far underlined the raging political animosity and uncertainty more than 50 days after an inconclusive general election.
The presidential vote is closely intertwined with the search for a stable government capable of combating a severe economic recession in the euro zone's third largest economy.
Prodi won only 395 votes, well short of the absolute majority of 504 he needed, indicating that center-left rebels had again disobeyed party orders in the latest of many rebuffs for Bersani. Around 100 center-left parliamentarians appeared to have refused orders to vote for Prodi.
Berlusconi's camp said that if Prodi was elected this was likely to prevent any government being formed and would push Italy towards new polls, possibly as soon as late June or early July.
A crowd of around 200 anti-Prodi demonstrators protested outside parliament and several parliamentarians led by Alessandra Mussolini, the granddaughter of fascist dictator Benito Mussolini, wore T-shirts marked "Not this" and "The devil wears Prodi".
The election of the next head of state to succeed Giorgio Napolitano, whose term ends on May 15, is a major step in efforts to break the stalemate since elections in February which left no party able to govern alone.
Italy has been without an effective administration for months while the election campaign and the long deadlock since have stalled any action to combat a recession that matches the longest since World War Two.
But the bitter battle over the presidency has underlined how hard it will be to reach political consensus on anything, let alone vital economic reforms or changing an electoral law that is one of the main causes of the current impasse.
The election left the center-left as the biggest group in parliament but its failure to win a majority handed Berlusconi decisive influence over the negotiations for both a new government and the next president.
The former prime minister has repeatedly said the nomination of a broadly accepted presidential candidate was the only way to form a government capable of addressing Italy's problems and avoid an immediate return to the polls.
He has several times rejected his old adversary Prodi, 73, an internationally recognized figure who is currently the United Nations envoy for Mali and the Sahel region.