Mélenchon is not "left" - he's far-left.

It remains extremely likely Macron and Le Pen will be the finalists, despite Mélenchon's rise - he might push Fillion into fourth, but he has limited potential draw left. He gets into the final round only if a scandal takes out Macron. The final, like almost all French presidential elections, will come down to one right wing candidate and one left wing candidate.