The ‘senile Joe’ mantra is set to backfire against us. Set the bar low and come on strong easily exceeding it. It
may be different this time around as the decline in mental acuity only gets worse as time goes on. However, you raise good point in that the Trump team needs to do much more than point the finger at senile old Joe. Remember in 2012. the common wisdom(especially around these parts) was that the new golden boy, Paul Ryan, would "eat Biden's lunch" in the VP debate. Granted, that was 8 years ago but the point was the GOP convinced themselves that there was no way this bumbling old gaffe machine could take on the new golden boy Paul Ryan in a debate. The perception by most observers, including most honest conservatives, is that Biden handled him easily and dismissively laughed in his face.
The only reason I bring that up is to caution against over confidence.
Biden handled him easily and dismissively laughed in his face. The dismissive laughter is one of Biden's standard tools, sort of like wood filler for gaps, he tosses it in when he has no good answer. Only now he doesn't pick the best moments to use it. Example: the "are you a junkie" interview.