One thing I'd add about the "shifting dynamic" around Biden's age is that many of these stories share a chronology: recent "weeks and months"/"since the previous fall"/"since last summer." There's reason to blame staffers, but as anyone with old relatives knows, the decline can be out of the blue.
Exactly. No expert, but lived it with relatives, not clear when occasional “what’s his name” becomes full fledged confusion. And deterioration can be very nonlinear, with long plateaus followed by sudden decline. He may have been fully up to the job when the decision to run was made say a year ago.
Exactly. An older person can be in fine health right up until the moment they aren't.
So cries of "Why didn't you see this coming?!" don't land when there was nothing to see.