Macron was never in any of Hollande's cabinets as a member of the Parti Socialiste, he was in fact an independent in all of them (last time he was a member was way back in 2009, way before Hollande was even elected). But besides all of that his economic positions can hardly be considered as lefty.
And I still believe the ACTUAL left has a chance if Hamon (PS) and Mélenchon (Front de Gauche) can come to an agreement. If polls are anything to go by, together they'd be credited with over 25%
macron presented himself all the way as a leftist, until couple of months prior to the elections, in a bid to gain more votes, he now pretends to be everything everyone wants him to be.
In his book Revolution, published in November 2016, Macron presented himself as both a "leftist" and a "liberal"
if he presents himself as a liberal leftist, then
maybe this is what he is in reality.
even in all the older
polls prior to his announcement that he was an independent, macron is listed as a potential parti socialiste candidate, all the way until august 2016. it was a smart move from his side, but i suspect that his numbers are still quite inflated, even with the support of bayrou i expect he will land two or three points behind fillon when the elections come.
i do not think melonchon and hammon can get along together, chances are they will not manage to present a unified front, in the second round both their votes will go against Le Pen, this is the closest they will get to an understanding it seems.
there are my personal expectations, but again, only time will tell.