Never thought of her as being "nasty" but maybe you know something that I haven't seen.

I believe that Trump is tired and wants a break. He has been hitting the circuit hard and fast as well as attempting to keep up on his social lifestyle. He was bound to crash sooner or later. Better to avoid the debate, than to attend and then hose it up. I believe that it will hurt him a bit, but he has a cushion as far as the lead is concerned. Cruz is getting desperate and has probably peaked. If he doesn't get it under control, he is going to say something more to hurt himself.

Rubio is steadily moving forward. Right now, Rubio is the best choice, in my opinion.