It’s amazing because you can watch him in real time start to give the details of what he imagines the test to be but then realized he doesn’t actually know anything about what the test is like and so pivots to not giving any details.
He’s a terrible liar, but he’s very good at exposing just how willing human beings are to let powerful people get away with lying, no matter how obvious.
The moment he gave that answer, if you actually wanted to expose his lie, just keep asking him specifically what the procedure was. Describe it for the American people, Mr. President. Some people don’t know what it’s like. Can you help them understand what to expect?
What my novel presupposes is ... what if he didn’t? 
He said it was nothing he ever wanted to go through again before drifting off into vague remarks, so I’d say he managed to scare people much better than he could have by describing it fully—which he clearly was not capable of doing.
I can tell you who pretty obviously didn’t know that.
People arguing over whether or not the swab test is or isn’t painful are missing the salient fact, which is that Trump clearly realized halfway through his story that he didn’t know the facts of the story he was about to tell, and he was telling people whose job is knowing facts.
