(By Paul Virgo) Rome, April 20 - President Giorgio Napolitano became Italy's first head of state to be re-elected on Saturday after he agreed to stand in the sixth presidential ballot in a bid to end political chaos. Five previous ballots failed to elect a successor to the 87-year-old because rifts within the centre-left Democratic Party (PD), the biggest group in parliament, saw two of its own candidates scuppered. The chaos-hit PD was joined by earlier on Saturday by ex-premier Silvio Berlusconi's People of Freedom (PdL) party and outgoing Premier Mario Monte's Civic Choice party in asking for Napolitano to stand again. The PdL's regionalist ally, the Northern League, voted for Napolitano too and he prevailed with a big majority, winning the votes of 738 of the 1,007 so-called 'grand electors', Napolitano, a former member of Italy's Communist party whose first seven-year term was due to end next month, had repeatedly ruled out staying on in the past. The deadlock over the head of state was threatening to further complicate efforts to end the political impasse recession-hit Italy has endured since February's inconclusive general election. The president has a key role in orchestrating efforts to form a new government in a hung parliament. Napolitano said he faced a "difficult challenge at a crucial moment" after being re-elected. He also called on "everyone to honour their duties" to "reinforce the (country's) political institutions". He now must get back to working on ending the impasse and see which parties are willing to form a government on the basis of a programme he asked to be drafted by a group of experts. Napolitano said he would give more details about how he intends to set about this on Monday. The president will face a stiff challenge in brokering solutions to create a new government, given the rifts within the PD, which led the alliance that came first in February but failed to win a working majority in the Senate. The party is set for a leadership contest as Secretary Pier Luigi Bersani said Friday he would quit "one minute" after the presidential election after rebels in his own party sank the candidates he proposed to Upper and Lower House lawmakers and representatives of Italy's regions. On Friday around 100 of the centre left's 'grand electors' failed to vote for ex-premier Romano Prodi in the fourth presidential ballot. Bersani presented Prodi's name in an attempt to regain PD unity after many in the party on Thursday did not vote for the previous candidate he had proposed, former Senate Speaker Franco Marini. The outgoing PD chief was already under fire for his handling of the post-election impasse. Italy still has no government as Bersani failed in a bid to reach out to the anti-establishment 5-Star Movement (M5S), which holds the balance of power in the Senate. He refused to consider forming a broad coalition government with the PdL, while at the same time rejecting calls for another vote, saying that this would be equally inconclusive under the current election law. Bersani's exit could make way for the PD's Florence Mayor Matteo Renzi, a telegenic 38-year-old who has been compared to the young Tony Blair and came second in the centre-left's premier-candidate primary in December. Renzi, whose loyalists led the rebellion against Marini, is currently the country's most popular politician, according to opinion polls, but he is viewed with suspicion by many in the PD. M5S leader Beppe Grillo called Napolitano's re-election a coup and called on "millions" of Italians to join him in a protest in Rome. But he then announced he would not be in the capital in time to lead the protest on Saturday. M5S candidate Rodota' also had the support of the left-wing SEL, which was allied with the PD in February's election.