By Nicholas Vinocur
PARIS (Reuters) - Francois Hollande's victory in a left-wing primary gives him the best chance in a decade of bringing the French Left to power, but he will need to rally rebel groups and clarify his policies to fend off charges of weakness.
The mild-mannered Hollande showed he could bring together a fractious center-left on Sunday when he beat Martine Aubry, the Socialist party chief, by a wide margin in a primary run-off that drew nearly 3 million left-wing voters.
Hollande embraced his defeated rival after she threw her support behind him in a concession speech. Yet the show of unity after his victory did not include the Left Party or the Greens, whose support is key if he is to beat President Nicolas Sarkozy in a 2012 election.
Far from falling into line, the leaders of both parties want clear pledges from Hollande on issues that matter to them: an exit from nuclear power for the Greens' Eva Joly, and higher capital gains tax for the Left Party's Jean-Luc Melenchon.
Arnaud Montebourg, an anti-globalization candidate who took 17 percent of votes in the primary's first round, said he backed Hollande personally but asked him to promise that he would bring French banks to heel if elected.
"Hollande's fairly moderate position on many subjects -- the issue of banks is particularly sensitive nowadays -- sets him on a collision course with the (more left-wing) groups that were deprived of media attention during the primary season," said Jerome Fourquet, analyst at the IFOP polling agency.
"Aubry was much more compatible with the Greens, for example... There will have to be a process of harmonization of positions if they don't want the base to fracture," he added.
"PURPOSEFUL" LACK OF PRECISION
So far Hollande has said he would tighten supervision of bailed-out banks, pare France's reliance on nuclear energy to 50 percent of its consumption by 2025 from 80 percent at present, and make taxation fairer. He did not, however, provide details about how he would enact such policies.
In a first shot over the bow after the primary, the Greens' Joly told Le Monde in an interview that the Left would be "crazy" not to make a complete exit from nuclear power. Meanwhile, Melenchon has branded Hollande's program a "minimum solution for the left."
On the financial front, Hollande has resisted prodding from Montebourg to agree that a government official with the power of veto should be placed on the boards of bailed-out banks, despite polls showing that a majority of left-wing voters favor nationalization.
In an orthodox step without precedent for a Socialist candidate, Hollande pledged during his campaign for the primaries to balance France's budget by 2017 if elected, but again stopped short of detailing how he would do so.
Pollsters say that Hollande is being vague intentionally to avoid alienating left-wing voters, or provoking the sort of internal strife that many on the Left say cost Segolene Royal during her 2007 presidential run against Nicolas Sarkozy.
"He has to be careful not to start too soon, not to unveil everything six months before the election," said Bruno Jeanbart at pollster OpinionWay. "It's fair to say that his lack of precision is purposeful, to better prepare for what's ahead."
Still, as the Left's clear front-runner, Hollande will have to define his positions more clearly before he faces off against President Nicolas Sarkozy in an April, 2012, election.
An October 1 survey by pollster LH2 shows Hollande beating Sarkozy with 31 percent of votes versus 21 percent for the incumbent. Eva Joly and Jean-Luc Melenchon are poll at 7 and 8 percent, respectively. Hollande is seen beating Sarkozy comfortably in a final round.
Even if a significant portion of Hollande's supporters defect to Joly and Montebourg, he would still clear the first round of the presidential election. But he is counting on their support to create a majority in the race against Sarkozy.
"The left cannot afford to repeat the divisions of the past," said Francois Miquet-Marty, an analyst at pollster Viavoice. "And it's possible for them to rally together today because the context has changed, the candidate is no longer Segolene Royal, who was a divisive figure."
KNIVES DRAWN FOR SHOWDOWN
With Hollande now the sole Socialist Party challenger, he faces attacks from a ruling party that has been weakened by the loss of its Senate majority and a series of corruption scandals engulfing Sarkozy's closest allies.
In late September, Sarkozy's conservatives lost control of the Senate for the first time since 1958. Many in France hailed the historic victory as paving the way for a Socialist presidency next year, which would be the first since the end of Francois Mitterrand's presidency in 1995.
Yet many in Sarkozy's camp say they relish the prospect of a drawn-out boxing match between the incumbent and Hollande, whose popularity at home is offset by a low profile abroad.
"I am happy to have him as an opponent," Henri Guaino, a close advisor and speech writer for Sarkozy, told France Inter radio. "He is someone who is extremely cautious, quite orthodox and not at all someone who pushes limits."
Attacks on Hollande -- who was Socialist party chief for 11 years but has never been a government minister -- flew during the primary as Aubry branded him a standard-bearer for the "soft" Left and "the establishment's candidate."
"The fact that some of these arguments are coming from the Left give them the aura of truth," said OpinionWay's Jeanbart. "The fact that Martine Aubry has spelled out a series of character faults makes them look authentic... That is sure to mark the presidential campaign."
Sarkozy, who has yet to declare himself a candidate, is effectively already in campaign mode, traveling around the country to meet with workers and farmers as he sets the stage for a tough battle for re-election in 2012.
His advisors will set Sarkozy's experience leading the country through a financial crisis in 2008-9 against Hollande's relative lack of international experience, starting with a television special devoted to the economic crisis on October 24.
Jean-Francois Cope, head of the UMP ruling party, is presiding over a party summit on Tuesday that will take Hollande to task over his plans to add 60,000 teaching jobs by 2017, tighten control of banks and boost youth jobs as unrealistic and incompatible with the need for fiscal restraint.
"I have the image of someone who has a lot of trouble taking tough decisions," Cope said on RTL radio. "We have stood by for two months as the Left spoke only to left-wing voters."
"Now it's time to get serious."
(Editing by Daniel Flynn and Jon Boyle)