I"ve cared for people with dementia for decades. If anyone shows signs of early stage dementia, it's not Biden, it's the former president. He has a terrible short term memory and he bragged about passing the very simple cognitive test that is sometimes used to screen for dementia. I would be embarrassed to brag about passing the "mini mental test", as it's often called. He acted as if passing that test means he's a genius. Sure, being about tor remember a bunch of simple words for a few minutes means you're a genius. I've never understood why so many people don't realize that Trump suffers from symptoms of at least one personality disorder, as well as possible symptoms of mania.
With Trump, he's playing a character...even though he doesn't seem tor realize it. I've mentioned it before but in the Netflix series "Dirty Money" episode about Trump, two people who helped create The Apprentice said that they basically created a sort of parody of Trump. When they met him, he was a bankrupt, washed up shell of what he used to be...working out of a messy, poorly maintained office in Trump Tower, and reduced to doing commercials for fast food and pizza chains.
So they created this role for him. A version of himself that was still successful, admired, on top of the world, and with young executives lining up for just the chance to work for Trump. Problem is, he actually believed he was that character, and has been playing it ever since.
And as with other performers who know their role very well, he's able to be "on" when needed. Think Ozzy Osborne. He's been ravaged by substance abuse, stammers when talking to the point of being unintelligible, shakes, and shambles along slowly. Yet when he gets onstage, he is suddenly this larger than life figure who gets the crowd going. His onstage persona takes over, and he becomes a rock god for a couple hours a night. Anyone who's done any kind of performance (acting, music, comedy, etc) can tell you that even if you're tired, sick, or hungover, once you're "on" it can all go away so you can do the show.
The Trump supporters, like the man himself, fully buy into the character he's playing when he's at a rally. Unfortunately there's no separate "reality" show where we hilariously watch Trump fumbling over words, forgetting names of people he's known for years, and lashing out at anyone who he thinks is treating him wrong. We've had a few books come out that describe the "real" Trump as a man with decreased cognitive abilities and a tenuous grip on reality, but they're dismissed by the faithful as the work of "disgruntled" people who are "losers."
As for the term limits thing? I like a line from the movie "Dave," where a Presidential look-alike takes over for the real one when he goes into a coma. "I was hired to do a job, and it's a temp job at that." I wish more people would look at politics as a temp job. You do your stint as a public service, then go back to your "real" job. Unfortunately, lobbyists and Super-PACs are not term limited. If we imposed term limits on elected leaders, we'd have to do some serious reform of how campaigns are financed, or the lobbyists would run rings around perpetual freshman Congress critters.