PARIS (Reuters) - Two left-wingers in France’s presidential race refused to call a truce on Thursday in a battle that looks sure to knock them both out of a contest that polls say will be won by centrist Emmanuel Macron in a runoff versus far-right leader Marine Le Pen.

Socialist Benoit Hamon vowed to fight to the end despite being deserted by key members of his party while hard left rival Jean-Luc Melenchon, buoyed by a poll surge, ruled out a merger with him that could put the Left back in play.

With the left-wingers locked in a seemingly suicidal combat, Macron relished announcements by several right- and left-wing politicians, including Socialist defense minister Jean-Yves Le Drian and Socialist ex-prime minister Manuel Valls, that they would vote for him instead of Hamon.

“I have a problem in politics at the moment: there are lots of people backing me,” joked Macron, a 39-year-old who promises to transcend the Left-versus-Right divide of politics in France, where the jobless rate in a sluggish economy is near 10 percent.

“That said, there’s some consolation in the fact that for others the problem is that people are leaving them,” he said at a meeting between candidates and farming sector representatives.

Hamon’s struggle - his potential score of votes is hovering slightly above 10 percent - is complicated by the defections of Socialist party grandees, not to mention competition outside his party from Melenchon, who has overtaken him in several polls of voting intentions.

Furious at Valls’ decision to defect to Macron, Hamon told public service radio channel franceinfo: “Of course I will stay through to the finish.”

Melenchon, a political veteran whose potential election score in polls has risen to as high as 15 percent in the past few days, several points above Hamon, said on Wednesday he was not going to bow out in favor of a single Hamon candidacy.

“I will negotiate with nobody,” he told a rally in the city of Le Havre. His spokesman said the Socialist Party, long split between moderates and hardliners, was now as good as dead.

Only the two top candidates in the April 23 opener go on to the May 7 runoff. Opinion polls put the two frontrunners - Macron and Le Pen - in the mid-twenties, way above those of Melenchon and Hamon and ahead of erstwhile favorite Francois Fillon, a conservative former prime minister.

A Harris Interactive poll found that 53 percent of voters felt Hamon should pull out of the race in favor of Melenchon, a firebrand left-winger who quit the Socialist party several years ago and is now candidate of the Left Party, or what the French call “the Left of the Left”.

A Kantar poll showed Melenchon apparently enjoying a late surge in popularity, with a 19-point rise putting him at the top of a popularity league ahead of all others in the election race. That poll did not measure voting intentions.

Sandwiched between the trailing leftists and the two leading candidates in the polls, Fillon vowed too to fight on despite a financial scandal.

Fillon said he would overcome damage inflicted by a judicial inquiry into allegations he paid his British wife and children for minimal assistance work in a misuse of hundreds of thousands of euro of parliamentary funds.

“I can look you straight in the eyes and say: the examining magistrates will never prove that my wife’s job was a fake,” Fillon told RTL radio.