By Brian Love
PARIS (Reuters) - France's Socialist Party named its new chief on Tuesday, a one-time political opponent of President Francois Hollande who will have to overhaul a ruling party reeling from local election losses in time for European parliament elections in May.
Jean-Christophe Cambadelis, 63, was elected by the party's national congress to replace Harlem Desir, weeks after local polls in which the Socialists lost dozens of towns to the right and far-right opposition.
Cambadelis faces the task of quieting dissent from the party's far left and avoiding further humiliation in European parliament elections on May 25.
He takes over a party in crisis, split between a core that supports Hollande's shift towards supply-side economic policies and far-left factions which strongly oppose it, with little time to enact his mandate of modernization.
"It should be up to the party's supporters to decide on its future," said a group of left-wing Socialists who previously signed a petition opposing Hollande's reform plans.
Infighting could further damage the party ahead of the May election, where Marine Le Pen's anti-EU, anti-immigrant National Front party is expected to do well, with Hollande scoring low in popularity polls after failing to bring down high unemployment.
One survey by pollster Ifop this week showed the National Front coming first in the European election with 24 percent of the vote, ahead of the center-right opposition UMP with 23 percent and the Socialist Party third with 21 percent.
Cambadelis, who made his mark as a student union leader in the 1970s before joining the Socialist Party, is returning from the cold after he failed to support Hollande during a party primary ahead of the 2012 presidential election.
Having backed his friend and ally Dominique Strauss-Kahn, who was once favored to win the nomination, Cambadelis switched his allegiance to Lille mayor Martine Aubry when Strauss-Kahn was forced to drop out of the race after a New York hotel maid accused him of sexual assault. Criminal charges were later dropped.
The choice ruled out any post in Hollande's government.
Cambadelis gained clout within the Socialist Party in the 1980s when he helped former President Francois Mitterrand seek re-election, later growing close to former Socialist Prime Minister Lionel Jospin.
But his rise through the ranks was halted in 2006 when Cambadelis was found guilty along with several other Socialists of having used a student mutual fund for political purposes and given a suspended jail sentence.
(Reporting by Brian Love and Elizabeth Pineau; Writing by Nick Vinocur; Editing by Janet Lawrence)