The whole "we can't let FN win" is going to have a wrong impact again. Just like we saw with Brexit and Trump. Give people your solutions and answers, don't just point to the other side and say "they are bad". If people vote FN there is a reason for it. Tap into that reason, but with actual better solutions.
So basically be nice to those that wish to put you in a camp, and really hurt you? The ones that don't care one bit for you, and are not interested in your solutions? The ones that wend out in droves to Paris to "stop gay Marriage!"? The ones.. yeah I can go on for a while...believe me these people will always vote Le'Penn as they are shitheads to begin with.