Trump doesn't "simply" do anything. He throws bombs. He cannot restrain himself, as we've already seen since yesterday afternoon. For a country desperate for leadership/consistency/competency this is a very tired look from a very tired, old man who looks worse and worse each time he goes in front of a camera.Trump will simply point out Harris' issues and the likelihood of her being President by default if/when "Sleepy Joe" dies. And she as a character is a bit of a firebrand and will double down on her radicalism when challenged.
It's one of several reasons why I can see easy Trump inroads into Bidens current lead.
Talking smack about Biden's health is pure projection.
Kamala Harris is seen as a "radical" only by those who were already going to vote for the current Administration. "Nasty woman" who is a "radical leftist" is not a winning strategy to bring back those who already laid a heavy judgment on him in 2018 or inspire new voters to his cause in the midst of a pandemic and economic catastrophe. Especially given it is so easily refuted.