Josh Marshall explains why:
The big problem for Newt is that Republican power brokers will not let him within 30 miles of the Republican nomination. A win is just too close. Why throw that away on someone as toxic, erratic and unpopular as Newt? Newt is a creature of the conservative Id, churning with resentment and provocation. Someone like Mitt can learn the buzzwords. But it’s Newt’s world. He half created it. Mitt may have to live there with him for the next several months. But politically Gingrich has never able to live outside of that world. In the end, he won’t beat Mitt because he can’t beat Obama.
The Dish 