By Barry Moody
ROME (Reuters) - Pier Luigi Bersani is in pole position to become Italy's next leader after winning a center left primary vote, but the former communist must now convince nervous markets and conservative voters he won't drag the country too far to the left.
Bersani, 61, crushed a challenge from Matteo Renzi, the youthful mayor of Florence, in a run off primary election on Sunday to choose the center-left candidate for a national vote next spring. He won more than 60 percent to Renzi's 39 percent, taking every region except the challenger's Tuscan home turf.
Bersani is often portrayed as a colorless career apparatchik, but his insistence on holding elections on the center-left against opposition inside his Democratic Party (PD) was a masterstroke.
It left him as unchallenged leader of the notoriously factionalized center-left, which itself emerged reunited from a vote that garnered extremely valuable public exposure.
Some three million voters participated in the second round and nearly four million in the first.
Debates between the candidates attracted record television ratings and reignited public interest in the traditional political system, which is under serious threat from the populist 5-Star Movement of comedian Beppe Grillo.
Latest opinion polls show the center-left gaining on the back of the primary process and a small drop in support for Grillo, who has ruled out any post-election alliances and wants a referendum on whether Italy should leave the euro. His movement is now running second.
With the center-right reduced to shambles by the indecision of former Prime Minister Silvio Berlusconi, who is still dithering over whether to stand in the general election, Bersani appears to have a clear run at becoming prime minister.
But he will soon face a series of tough challenges.
Above all he must convince the conservative voters who dominate Italy that he is not a dangerous leftist and persuade investors he will not dump the painful progress made by technocrat Prime Minister Mario Monti in rescuing Italy after it came close to a Greek-style collapse under Berlusconi.
Bersani has repeatedly pledged to stick to Monti's tough budget commitments, which have calmed the markets, but says they must be tempered with policies to boost growth, reduce unemployment and ease the pain on workers and pensioners.
Bersani must also find a way to end divisions with the large bloc of Renzi supporters and exploit the modernizing Florence mayor's appeal to center-right supporters - perhaps by offering him a party post after the bitterness of the contest subsides.
Senior PD officials have told Reuters they see the rise of anti-establishment, anti-European forces as their greatest challenge, together with wooing the nearly 50 percent of voters who say they will abstain or have not decided how to vote in an election expected in early March.
"The primaries were very far-sighted. It was the only way to combat Grillo," PD deputy leader Enrico Letta told Reuters.
Critics say Bersani beat the challenge from the dynamic, telegenic Renzi, 37, only by his control of the traditional party machine and making a deal with Nichi Vendola, the head of the leftwing Ecology and Freedom party.
They say most of Vendola's votes in the first round went to Bersani in the run-off and he will want payback.
Bersani aides say Bersani headed off this danger by making all primary candidates, including Vendola, sign a binding pact to abide by majority decisions in a center-left government.
"This is a central point. The undertaking to accept a majority vote on crucial questions," Letta said.
But center-right politicians and other critics are skeptical. "Vendola wants to dismantle the Monti reforms....even if I was convinced he would keep his promises he will not be in a position do so," said senior PDL politician and former Foreign Minister Franco Frattini.
Others are more sanguine, pointing out that Bersani supported Monti's reforms as part of a grand right-left coalition and big changes would quickly put Italy under renewed pressure from rising interest rates as markets took fright.
They also say Vendola's bark is worse than his bite and that he has pursued moderate policies as governor of the southern region of Puglia since 2005.
"I don't see a specter of Vendola even for the markets," said a senior Italian financial official who asked not to be named. "A return of Berlusconi would be much more of a specter than Vendola."
Center-left officials say Monti's success has in any case been greatly circumscribed by his need to get approval for all his measures from a squabbling group of politicians in an uncomfortable cross party alliance and that a prudent elected government could do better.
"In the next legislature we must impose policies of austerity, yes, but also growth. It is a long road. If you only have tax and austerity, it is predictable that voters deprived of light at the end of the tunnel either join the populists or abstain," Letta added.
Bersani was quick to warn his ebullient supporters after the primary victory that the road ahead would not be easy. "We must give the center-left a strong profile for government and change. We must succeed without telling fairy tales," he said.
(Editing by Philippa Fletcher)