Don't trust opinion polls! Le Pen is the comparatively unacceptable face of the 'anti-establishment' parties, whereas Macron is standing on the same platform with a more acceptable line. Le Pen is drawing on the instability of Fillon's campaign and the allegations of corruption surrounding him. However, Le Pen is herself an establishment figure and it is inevitable that the French public would want to signal their disapproval of the mainstream for the time being.
"The first round of the elections is always an opportunity for protest, but then voters have their minds focused in the second round. I'd still expect Macron to pull through, but there's a reason why some newspapers in France have stopped commissioning polls - we could be looking at some shy Macron supporters unwilling to voice their support until after the first-round in April.
"Macron's visit to Theresa May has reinforced his image as a statesman, and this is something that Le Pen simply cannot rival. Opposition to the EU is one thing, but Macron's image is one of stability based on a track record, the Le Pen project is a mismatch of competing policies, very few of which make sense."
Dr David Lees Teaching Fellow in French Studies