Biden has long been known for verbal mixups. These likely result from the fact that he has overcome a serious stutter, so his verbal processing is more convoluted in his brain that those of us who have not had to contend with that issue. Voters will have to decide what concerns them more, the occasional gaff such as saying Mexico when you mean Egypt, or Trump repeatedly confusing Nikki Haley with Nancy Pelosi, or insisting that he ran against and beat Obama, or that Washington won the Revolutionary War by taking out British airfields, and on and on.
I do wish the Ds had come up with a younger, more dynamic candidate. I think Biden has done a pretty good job, considering all the obstacles and crises he has had to contend with, but at this point he looks and sounds really old. That is superficial appearances, but it unnecessarily concedes some ground to Trump. I hope it doesn't turn out to be like Ginsberg hanging on a little too long.