Don't hold your breath for anything positive for Trump emerging from these debates. They will shoot Biden up with something that makes him coherent for two hours, some drug that cannot be administered too often, or else it makes things worse.
Biden will most likely hold his own with the softball questions he will receive. And Trump will receive questions like, Mr. President, why did you murder 225,000 Americans with the corona virus? etc.
Trump needs to stick to basics, decry the Biden desire to increase taxes, to implement the Green New Deal that would end cows, planes/jets, fossil fuel, cars etc. A great commercial would be showing California with no electric, and show a map of the USA going dark if the GND gets implemented under a Biden presidency.