yeah Gary's support would drop like a brick.
Nah, I don't think that's how it works. Unless he eats a baby on live TV or something, the mere fact that he was invited to appear on stage with the other two would elevate him as someone who some unhappy-with-both-major-parties voters would consider voting for.
So even with a very bad performance, I think he would have done a bit better on Nov. 8 than he does IRL with no debate appearance.
Normally, you would be right but we're talking about a guy who does stuff like this, as well as this kind of...thing. I really think you'd see a stampede of uneasy Johnson supporters back to the Republican ticket.
It's not like Trump or Clinton were stable or well-liked, and Johnson just being on that stag would convince many to take a third option rather than two historically unpopular candidates.