Wait a minute here, folks. I just watched most of Biden’s meeting with Zelenskyy in Paris and was taken aback. Biden seemed old, stiff, spoke softly and haltingly at times. If that’s how he is at a debate, contrasted with Trump’s loud, aggressive style, it will not go well for Biden no matter how good he is in terms of thoughtfulness and coherence.
Seriously, I think Biden on the whole is doing a good job and deserves reelection even aside from the horror of a Trump second term. But the physical contrast would not be good.
ETA: I like @Spoons’ idea of an interview if Trump bails at the last minute.