Chris Christy gave tRUmp only one piece of advice as debate coach:

“People who overcome stuttering have a harder time maintaining their train of thought when interrupted. Keep interrupting him and he’ll stumble when he tries to speak. This will enforce the ‘senile’ narrative.”

It is a well-known tactic used by investigators, unscrupulous debators & vulgar bullies. Both tRUmp & Christy qualify for that label. If you listened to Christy on ABC after, he went straight for the stumbling talk of Biden claiming lack of coherence. No one else saw it that way.

It was a terrible & intentionally cruel thing to do, which is exactly why you know they planned it. Just watching it triggered my PTSD. But it failed to accomplish what they hoped. Joe kept his cool even with a few stumbles. The difference between the two could not be more clear.