Rome, November 23 - Italy will not have national elections until the spring, but the nation's next premier may emerge this weekend at Sunday's centre-left primary. The main centre-left Democratic Party (PD) has a significant lead in the polls, so the winner will be in a strong position to be Premier Mario Monti's successor, although there are many uncertainties. Five candidates are running, but most commentators see the primary as a three-way fight between PD Secretary Luigi Bersani, young Florence Mayor Matteo Renzi and left-winger Nichi Vendola. Bersani is the frontrunner - his support levels among centre-left voters was hovering between 43 and 47% according to a poll released by the SWG agency on Friday, ahead of Renzi with 29-33% and Vendola third with 16-20%. Bersani is a veteran of Italy's former Communist party, the rump of which changed into a social democratic party after the fall of the Berlin wall before merging with the centrist Margherita (Daisy) party to form the PD in 2007. This makes him the favoured candidate of the PD's rank-and-file supporters, many of whom are former Communists, even though his leadership of the party has been criticised for being too timid since he became secretary in 2009. A former minister, he is considered a safe pair of hands. He can boast having preceded the sort of structural reforms Monti's emergency technocrat administration has been introducing over the last year. He was the architect of groundbreaking economic liberalisation legislation when he was industry minister in Romano Prodi's 2006-2008 government. Renzi, 37, is a slick performer with the media, who presents himself as a modernizer and is campaigning for Italy's political class to be rejuvenated. Some pundits have compared him to the young Tony Blair. His calls for the political old guard, including senior members of the PD, to be "scrapped" have struck a chord with many Italians. This is because there is widespread disenchantment with the established parties, which have been hit by a series of scandals and have been discredited to some degree by having to call on Monti's technocrats to take over governing the country when the financial crisis risked spiralling out of control last year. Otherwise, the policies he advocates are middle of the road, but more market-friendly than his rivals. Critics see him as little more than an upstart opportunist. Vendola, 54, is the openly gay governor of Puglia and the head of the Left, Ecology and Freedom party, which is set to be allied with the PD at next year's elections. While Bersani and Renzi have largely supported Monti's government, the big difference with Vendola is that he has been a staunch critic of the reforms and austerity policies pursued by the current government. He has called on the next government to drop Italy's austerity drive, so a win for him would probably alarm the financial markets. Also running are Bruno Tabacci, a member of the centrist Alliance for Italy party that is set to run in coalition with the PD, and Laura Puppato, a businesswoman and PD councillor in the Veneto regional assembly. PD Chairwoman Rosy Bindi has said one million centre-left supporters have already registered to vote in the primary and hopes over two million will take part. There will be a run-off between the top two candidates a week after Sunday's vote if no one claims more than 50% in the first round. Pundits think it likely Bersani will fall short of the 50% mark on Sunday, so he is likely to go into a run-off against Renzi a week later, where he would be boosted by Vendola's support. Around 30% of Italians intend to vote for the PD at next year's elections, according to recent polls. The second biggest group is comedian Beppe Grillo's anti-establishment Five Star movement, which is making big gains with the help of the skepticism about the party system that Renzi has also tapped into. Ex-premier Silvio Berlusconi's People of Freedom (PdL) party is third. So the PD is tipped to win next March's general election but it may not have enough seats to form a government on its own, at least if Bersani wins the primaries. Some pundits still see Bersani as Italy's most likely next premier if he succeeds in his declared aim of reaching out to centre parties. Several polls suggest Renzi is the candidate who would be most likely to land the centre left a majority it could govern with in national elections, as he would be able to appeal to traditional centre-right supporters disaffected with the PdL as well as as centre-left voters. However, with Italy's much-criticised electoral law still needing widely-demanded revision and the political scene in disarray thanks to the rise of Grillo's Five Star Movement and disillusion with the PdL, many pundits think current technocrat Premier Mario Monti may be asked to stay on. Monti has said he is open to serving again if there is a stalemate that would put Italy's hard-recovered financial credibility on the line. The former economics professor and ex-European commissioner has received backing for a second term from a range of Catholic centrist groups. The PdL is set to hold primaries to choose its premier candidate on December 16, despite the reservations of Berlusconi, who has said he will not stand for a fourth term at the helm of government. Over 10 candidates, including party secretary and favourite Angelino Alfano, are set to run in them.