Hard to see how Trump is stopped after winning the first two contests.
Cruz may have made it close in Iowa but will have poor numbers in NH and be dismissed as a one-state pony.
None of the establishment candidates will have come close.
Trump would get extremely favorable media coverage and tons of momentum, certainly win the next two states, and his national numbers would jump up to the 50s.
Basically this. while Trump still his problems is head to head matchups, remaining at best competative, there's still the question of who the anti-trump will be.