I watched the first ten minutes of the 'debate' and had had enough.
I don't know how many watched the ones prior and subsequent to this, but... 68m people (if I remember rightly) watched this.
The past four years don't mean much for the forthcoming election at the end of the year when the concerns of people are not being addressed, by someone who struggles to walk and speak coherently.
There are plenty of people worried about this, and calls for him to step down are significant. If he's like this now, what's he going to be like in his mid-80s? This does not look good.
You can say: the past four years! as much as you like, it won't matter if Biden loses, which is a more realistic prospect than it was last week.