By Leigh Thomas and Sarah White
PARIS (Reuters) - Centrist Emmanuel Macron and far-right leader Marine Le Pen still hold a firm lead over the pack in France's presidential election, polls show, with a surging left-winger becoming a wild card in the race.
An Opinionway poll on Thursday showed Le Pen and Macron taking 25 and 24 percent of the first round vote respectively, with the ex-banker beating the National Front leader by 60 to her 40 percent in the runoff - a scenario largely unchanged in polls since mid-February.
But while scandal-hit conservative candidate Francois Fillon was holding on to third place, 65-year-old Jean-Luc Melenchon, a veteran far-left maverick, has moved up fast in the ratings.
A Harris Interactive poll of voting intentions showed support for Melenchon climbing to 17 percent in the first round from 13.5 percent two weeks ago, after a televised candidates' debate on Tuesday night when he was rated the star performer.
The Harris poll had Fillon, whose campaign has struggled as he seeks to defend himself from nepotism allegations, holding steady on 18 percent.
Though Opinionway gave Fillon a higher, unchanged rating of 20 percent, it also had Melenchon on a higher rating of 16 percent, up one percentage point on its previous poll.
The two-stage election will be held on April 23 and May 7.
Macron, a pro-European former economy minister in Hollande’s government, seeks to transcend the traditional left-right divide in French politics and boost economic recovery by reducing public spending and cutting taxes to help business innovate
Le Pen wants to curb immigration, ditch the euro and bring back the franc, and hold a referendum on European Union membership.
Though it would take a collapse of the official Socialist candidate Benoit Hamon's campaign to make Melenchon a real contender for power, his surge in popularity complicates the calculation in an unpredictable contest in which more than one third of voters are still undecided.
A political showman who excoriates establishment politicians with his rapid-fire discourse, Melenchon was seen by pollsters as the most convincing performer in the four-hour TV debate that was watched by more than six million people.
He clashed with Le Pen during the debate over her focus on the tensions created by religion in politics, but his policies advocating greater worker protection, and his hostility to the European Union in its current form, are similar to hers.
He would also pull France out of NATO and called during the debate for the debt of troubled euro zone states to be effectively written off to allow massive new investment to spur growth.
Founder of the "France Unbowed" party, he has split the left-wing vote and turned the Socialists into also-rans after five years of unpopular rule by Socialist President Francois Hollande.
Melenchon appears to be gaining votes from Hamon, who is struggling to stay above a 10 percent rating in the polls, but he is also getting votes from further afield.
Gianni Pierson, 38, from the staunchly conservative town of Provins where Fillon campaigned on Wednesday, had traditionally voted on the right, and plumped for ex-president Nicolas Sarkozy at the last election in 2012.
Partly as a result of losing his job as a salesman, he has turned more to the left - first Hamon, but now, he told Reuters, he has "almost made my choice for Melenchon" after being inspired by his performance in debates.
In a potential boost for Hamon though, Socialist Finance Minister Michel Sapin confirmed on Thursday that he would vote for the party's official candidate.
Some other senior Socialists, including Defence Minister Jean-Yves Le Drian, have jumped ship to join Macron.
Click http://tmsnrt.rs/2lPduBG for graphic on French presidential election
(Writing by Andrew Callus and Richard Balmforth; Editing by Tom Heneghan)