If Trump does succeed in his presidency, it will look bad for Democrats. Since, it will discredit the bad things he's done. Democrats use his faults to further project their point of view. A usage of facts. Although, if he does something fruitful, like the tax cuts, (that's also decidable), he would get credit. In turn, the view on him will change. That would put Democrats at a disadvantage. Since, they thrive off of the back lash he gets.