I'm not sure if he's blowing hot air or if he really is going to be a no show? To tell you the truth, I doubt it will hurt him in any way at all. He's becoming quite the Teflon "DON'ald. I think he could walk out on the middle of the stage, take a big ol' crap and he'd go up by 3pts.
https://www.nbcnews.com/politics/first-read/fox-news-announces-lineup-thursday-s-gop-debate-n504831
https://www.nbcnews.com/politics/first-read/fox-news-announces-lineup-thursday-s-gop-debate-n504831