Communist-backed Mr Mélenchon has stripped the scandal-tarred right-winger of third place with 18.5 per cent of first-round votes, up 4.5 percentage points from two weeks ago, according to the Ipsos Sopra Steria poll for France télévisions and Radio France.
The embattled centre-right candidate is for his part expected to garner no more than 18 per cent of the vote in the election’s first round, which will be held on April 23.
François Fillon is now fourth-favourite to win after being overtaken by Jean-Luc Mélenchon
Independent centrist Emmanuel Macron and Marine Le Pen, the hardline leader of the nationalist Front National party, remain engaged in a tight battle for first place, and are both expected to garner 24 per cent of the vote in the first round of voting.
The poll also showed hard-left Socialist candidate Benoît Hamon lagging well behind in fifth place with a meagre eight per cent of the vote, down four percentage points in two weeks.
The poll found that Mr Mélenchon is expected to garner 18.5 per cent of first-round votes
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Mr Macron, however, remains favourite to win the presidency and is poised to beat Mrs Le Pen in the second-round runoff on May 7 with 62 per cent of the vote over 38 per cent for the far-right chief, according to the poll.
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Despite being less popular than their two nearest opponents, Mrs Le Pen and Mr Fillon have the strongest support base of all candidates, with 79 per cent of their sympathisers sure of their choice.
Emmanuel Macron and Marine Le Pen remain engaged in a tight battle for first place
However Mr Macron is expected to beat Mrs Le pen in the second-round runoff
Mr Macron’s support base, however, is far more volatile, with only 55 per cent of his voters sure of their choice.
Mr Mélenchon certainty score remained unchanged at 60 per cent, whilst Mr Hamon’s was down five points at 43 per cent.
The poll was conducted between April 7-9 among 1,604 registered voters.