The issue in general with populists is that you cannot beat them with facts, figures and actual policies because they dismiss all of that ("elitist", "the media is tricking you", etc) anyway and push the discussion towards low feelings. So either you stoop at that level (in which case voters will still follow the one who went that direction first) or you don't (and keep being called "disconnected", etc) and lose. That's how Bush led to Trump (with the Obama interlude), how Berlusconi led to Salvini, etc. The only difference, imo, is that Sarkozy did not lead Le Pen to being elected, but that's only because in the meantime you have something "new" (Macron) that appeared on the scene. Once you fall to populism, it's very hard to climb out of it.