Eschaton today has a post about Don Junior’s long-standing explanation for the June 2016 meeting with the Russians, and Trump’s tweet today demolishing that alibi. Don Junior says the meeting wasn’t about oppo on Clinton at all, that never came up, the meeting was about the Magnitsky Act. So today Trump tweets,
Fake News reporting, a complete fabrication, that I am concerned about the meeting my wonderful son, Donald, had in Trump Tower. This was a meeting to get information on an opponent, totally legal and done all the time in politics - and it went nowhere. I did not know about it!
You can definitely go very far towards explaining the variance from reality of all sorts of statements people, especially politicians, make, based on the idea that they are lying and/or BSing. For example, lately part of the standard response of R politicians and their apologists to the latest school shooting is to come out for arming teachers. That would be straight up insane outside the context of our politics. Inside that context, it's totally unremarkable, and not the least bit probative of dementia or insanity. It's just probative of utter disregard for the public welfare and utter contempt of the electorate.
So, sure, though just about everything Trump says is wildly disconnected from reality, most of that disconnection looks like standard R lies and BS. You don't have to bring in dementia to explain most of it. But the tell, the reason you can't explain the total package as standard lies and BS, is when Trump completely loses the thread of whatever strand of BS he's following, and says things to directly and categorically destroy the very thread of BS he is working to build up.
But even when he steps on his own lede like that, busts up his own line of BS, the last line of defense we have against the insight that our president really is just disconnected from reality, is that it was just a mistake, just sloppiness, such as even a cognitively unimpaired BSer will occasionally make, because it does get to be a tangled web, and sometimes the lines of BS cross, so maybe you have to give up one line of BS to preserve a more important one.
Well, when the line of BS he's working is the alibi he and his son need to keep him in office and both of them out of jail, then, no, you simply cannot claim that he is some BS master, not at all cognitively impaired, and he just slipped up in torpedoing this alibi, as he did in today's tweet, or as he did with Lester Holt over the Comey firing alibi. These alibis are the obvious, critical, lines of BS that he absolutely cannot let fail, and that no person who wasn't actually demented, would have just torpedoed because he forgot how important it was to stay out of jail, or how important keeping up the alibi was to that end of staying out of jail. That's the sort of thing you don't forget unless you're demented.