By Brian Love and Ingrid Melander
PARIS (Reuters) - Prime Minister Manuel Valls emerged on Friday as the possible standard bearer of the ruling Socialists in France's presidential election following Francois Hollande's shock announcement that he would not seek a second term.
A snap opinion poll, conducted on Thursday night after Hollande' statement, showed that Socialist voters and French voters as a whole wanted to see Valls win the party ticket to run for president next spring.
But the Harris Interactive poll showed that Valls, a centrist who is tough on law and order, has only a slim lead among leftwing voters over his chief rival Arnaud Montebourg, who is waging a stridently left-wing campaign.
The Socialists face a tough battle over whether they should be more centrist or veer more to the left to try and regain the popularity they have lost since Hollande was elected in 2012.
But Hollande's decision to bow out of the contest does not change the broad expectation that any Socialist candidate - Valls included - would be eliminated in the first round of voting in April, and that the president would be chosen in a May 7 runoff between conservative candidate Francois Fillon and far-right leader Marine Le Pen.
The left "is fragmented as never before. It's a pulverized landscape," Pierre Moscovici, a veteran Socialist, told Radio Classique. "We need to rebuild the left," said Moscovici, who is now an EU Commissioner.
The 54-year-old Valls is expected to announce his candidacy in the coming days, possibly at a left-wing convention in Paris on Saturday.
If he won the late January primaries, Valls would still face competition in the presidential election from other candidates on the left, including Jean-Luc Melenchon and former economy minister Emmanuel Macron.
There are also fewer voters on the left than four years ago.
"The pool of leftwing voters is shrinking and within that there is 'a war of the left' ... the rivalries are sharper than ever," said François Miquet-Marty of Viavoice pollsters. "There are about 22-23 percent of voters who say they are leftwing sympathizers, which is very low, while in 2012 that stood at around 40 percent."
A former interior minister who has been regarded as France's "top cop", Valls broadly represents the centrist economic stance that Hollande adopted two years into his term.
"I consider that Manuel Valls is the one who has the strength to do it (be a candidate)," Patrick Kanner, a government minister, told RTL radio.
But others, including Benoit Hamon, a candidate in the primaries, were quick to say that the Socialist Party needed to change its focus. Hollande's 2014 pro-business U-turn prompted many leftwing voters to turn their back on him.
Voters were disappointed, Hamon told RTL radio, adding: "The left must aim at social justice."
Several opinion polls over the past week show Valls faring marginally better than Hollande would have done, but still being eliminated in the first round of the presidential election
For the Socialist primary next January, a Harris Interactive poll showed Valls on 24 percent, versus 14 percent for left-wing firebrand Arnaud Montebourg, and much smaller numbers backing the six other candidates.
But 47 percent of people said they did not want any of the eight so far in the running in the Socialist Party primary.
And when asked only if they preferred Valls or Montebourg, some 47 percent of leftwing sympathizers said they would chose Valls, barely ahead of Montebourg's 45 percent.
Montebourg, who is campaigning on the need to protect French industry from cut-throat global competition, faced off against Valls in the primary that Hollande won in 2011 before going on to beat Nicolas Sarkozy in the 2012 presidential election. While both Montebourg and Valls were eliminated, the former's score was more than three times that of Valls.
(Reporting By Johnny Cotton, Matthias Blamont, Simon Carraud, Emmanuel Jarry; Editing by Richard Balmforth)