Negative ads work, my friends. Those of you saying that there'll be some kind of backlash against "the establishment" for running these ads...yeah, right. Who the heck even pays attention to the name of some pseudo-anonymous Super PAC running ads like this? People just watch the ad and absorb the message, without paying attention to who is funding it.
That said, you can't beat somebody with nobody, and Trump has plenty of $ to retaliate. He can fund his own negative ads against Carson, or Kasich, or anyone else who might threaten his position in one of the early states. So this is hardly some kind of sure-fire way to stop him in any particular state.
They'll also pillory each other even if Trump doesn't lift a finger. Not that he'd be able to resist.