And yet that 1.5% change made all the difference.

... or perhaps more to the point, WHERE that 1.5% change occurred made all the difference.  Clinton won California and New York in a landslide, as expected, but she lost Florida by a few votes while she was expected to win by 2 or 3 percentage points.  That small swing in Florida meant that 29 electoral college votes went to Trump instead of Clinton.

Does this apply in France's presidential elections where they do not have a state-by-state winner-take-all system?  Arguably not, but that isn't to say there isn't something else that may occur.  At the end of the day polls are just a guess.  Given that Marcon hasn't even released his policy plans it is pretty early for anyone to suggest he will win.