By Michel Rose and Andrew Callus
PARIS (Reuters) - Former prime minister Alain Juppe on Friday threw his support behind Francois Fillon's French presidential bid, hoping to heal party divisions days after he sharply criticized the conservative candidate in a speech.
Juppe, who was defeated by Fillon in the center-right primaries in November, had been seen by many conservatives as a potential 'plan B' after Fillon became embroiled in a scandal over his wife's pay.
On Monday he ruled out taking Fillon's place and a rebellion that was forming behind him fizzled out.
"Even if just a passenger, I'm not jumping ship during the storm," Juppe tweeted on Friday.
The move could help The Republicans come from behind in opinion polls by encouraging Juppe's more centrist supporters to stick with the party rather than switch to the favorite, independent Emmanuel Macron.
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Fillon now has a fine campaign line to tread because victory also depends on attracting voters away from the other leading candidate, Marine Le Pen, the far-right National Front leader.
Only two top candidates from a first round vote on April 23 will contest the second round on May 7. Opinion polls show Fillon coming third in the first round and Macron going on to become president.
Two polls on Friday showed Macron and Le Pen level in the first round vote with Fillon lagging well behind in third.
In his speech on Monday renouncing the chance to run, Juppe, the 71-year-old mayor of Bordeaux, had harsh words for Fillon, who expects to be placed under formal investigation over payments to his wife when he sees investigating magistrates on March 15.
Juppe accused Fillon of wasting the strong lead his party was enjoying before the scandal broke, called him obstinate, and expressed disquiet at his attacks on the media and judiciary investigating the case.
MACRON BROADENING SUPPORT
Polls have shown that some of those who backed Juppe are reluctant to support Fillon, offering an opportunity for Macron.
He has already this week won support from a former Communist party head, the previous Socialist mayor of Paris, a right-wing former minister, and is in talks with the popular outgoing Defence Minister Jean-Yves Le Drian.
Macron was campaigning on Thursday and Friday in Juppe's territory in Bordeaux, where he hailed Juppe as "a great leader" and dismissed left-wing and right-wing politicians for trying to place him in either camp.
"We have to build a majority for this project. Don't believe that the candidate of the left which is tearing itself apart can achieve it, but don't believe that the National Front candidate can build a real majority," Macron told a campaign rally.
"And don't think either that the sad candidate of the right that is uniting reactionaries and opportunists can build anything."
Macron, who was previously economy minister under Socialist President Francois Hollande, has faced blistering criticism since Thursday from Socialist candidate Benoit Hamon.
Currently lying in a distant fourth place, Hamon said Macron was "immature" and labeled his program dangerous for the country.
"I don't think he will be ready to tackle the challenge of being the head of state, which means facing the European question, Mr Trump, Mr Putin and especially facing his own people," Hamon told France 2 television.
(Editing by John Irish and Robin Pomeroy)