Look, I can testify from personal experience that speaking on live television is hard, especially if there are people watching. Your brain is constantly making a dozen contradictory calculations at once...How much time do I have? Do I answer the question literally? What's the broader point I should be making? Is there some juicy one-liner I absolutely need to stick in there? How do I differentiate myself from the rest of the panel? Am I remembering to smile? Speak in complete sentences and not like a Valley Girl? Relax, Matt, relax! So...very...thirsty....OH GOD WHAT DO I DO WITH MY HANDS?!?!? Sometimes you just can't talk good, or trail off sentences, or even admit to forgetting the question.
Whatever the cause, if you can't slap Mitt Romney silly for being a flip-flopping used car salesman, you can't win the GOP presidential nomination.