I think the case for Trump 2020 is the exact same case against Trump 2020: He is a terrible leader.
Those for him think that the executive branch has too much power and our daily lives are too dependent on one person elected by the masses being on point.
Those against him think he’s a terrible leader that will cause the collapse of the US as we know it and unnecessarily put peoples lives in danger moving us and the world back decades.
There are also those who are just strict Ds or Rs or single/few issue voters. They either don’t think he’s a bad leader or don’t care. But in a world where the vote is almost always 50/50 it’s more important to focus on the independent/swing voter mentality.