Biden's gaffes are at least partially due to his life-long battle against his stuttering -- a search for the word he wants to use. Yes, most of us my age have some level of diminished cognitive abilities, but the more universal issue is lack of stamina even under normal conditions. I cannot imagine how he could cope with the long-hours and multiple demands put upon that office -- particularly when traveling across multiple time zones -- without having handlers trying to triage demands upon him, and remind him what to do next. Even young executives need those type of handlers. Doesn't make him incapable as long as he has good staff. The old West Wing TV series comes to mind, where President Bartlett was battling MS (and his wife was an MD rather than a PhD).
To me it is more a question of the quality of the Cabinet officials who have the power to remove him, either through persuasion or using the 25th Amendment. Trump's tended to be sycophants, who now keep testifying they were sounding the alarms and trying to hold him accountable but only in 20-20 hindsight when their necks are on the line as well. Nancy appears to have shielded and protected Reagan so Cabinet officials would not see how bad his Alzheimer's had progressed. While Biden's Cabinet is far from Lincoln's Team Of Rivals, I have more confidence that they will step up if necessary.
And part of that confidence is that I think Dr. Jill Biden -- rather than being the shield Nancy was, or actual go-between that Mrs. Woodrow Wilson was -- would be one of the first to advise him that he might need to step down, or at least back for a bit -- another option under the 25th Amendment. Allegedly Joe was encouraged by her to run for President to fulfill the death bed wishes of his late son, Beau. If she sees that it is overwhelming him, I think she would be counseling him to do what is best for himself and the country.
