The fact that Amy McGrath is considered a "strong candidate" and McConnell is viewed as a "weak incumbent" by pundits shows you how meaningless, subjective, and utterly useless the candidate quality dichotomy (strong--weak, great--awful, good--bad) is. Just because he’s unpopular doesn’t mean that he’s an ineffective campaigner (far from it, actually).
I unironically believe that McConnell is a "stronger incumbent" than Gardner or Tillis despite being more unpopular. Shocker, I know.
McConnell is a weaker candidate than Gardner , its just that Garden is running in Colorado while McConnell is running in Kentucky