It was cringe-making. I think Carson failed to hear his cue above the applause and proceeded to stand there like a lemon, as did Trump. I did enjoy Jeb Bush's expression as he passed Trump - "F*ck you, I'm on".
I also heard on the radio today that Bush has one of the better factcheck records of the campaign, with Trump, Cruz and Carson all scoring woefully. Sanders and Clinton are about equal and way ahead of any of the GOP contenders in their veracity.