Subjective or objective "proof"?
Tell me what did you see both before and after the debate? Was he that bad before the debate or after the debate?
Ask your sister who is very knowledgeable on a personal experience level on diminishing mental capacities and a one off swing of that scale. It made my wife go "WTF just happened?"
As for WH medical staff? Why would they be jumping to blood and urine testing afterwards? Even if they did there are drugs/compounds with a half life of just minutes/hours.
The answers to weirdness in this political day and age are in the questions you don't ask.
When an anomaly like this comes along, question the shit out of it.
Tell me, was there a better way than utter humiliation to cast doubt on his capacities and throw the election?