the best answer i have for that is that i'm not in france. it's very hard for me to know the details of precise policy implications, and i'm not going to pretend i can tell french voters what is in their self-interest.
however, from a distance out here in canada (and i can at least say that i'm rather culturally aligned with the quebecois nationalists, even if i don't support independence, or the "quebec libre", as their dead fascist dictator once demanded), i would have to point out that the french "left" seems extremely right-wing, and the french "right" seems extremely left-wing.
i can at least tell you that, as a hard leftist, the french "left"'s recent embrace of the extreme islamic right and open support for right-wing terrorism doesn't seem very attractive to me, as a left-wing voter. it is the french "left" that is producing anti-semitic statements and has open bigots running for it, not the french "right".
this switcheroo is happening all over the world, one way or the other, sometimes incompletely, but it's pretty consistent.
that doesn't mean i'm going to sign up for french nationalism. i haven't signed up for quebecois nationalism, and it's a lot closer to me. however, i would ask any real french leftist to very carefully analyze it's temporary allies and determine which is closer to you ideologically and which is in truth a complete and total right-wing fraud.