He's already backed off of that. Exceptions to his "ban" are coming in by the hour. He knows he stepped in it but, see, he got his result. His fired-up followers never bother to notice that he later qualifies stuff like this.
What he got was nonstop media attention, which saves a lot on advertising.
I rarely listen to the Glenn Beck show, but his sidekicks Pat and Stu said something today that merits consideration: one thing that never comes into play when Trump says something or comes up with a "policy" is the Constitution.
The Democrats ignore the Constitution, certainly. Many now are saying it's irrelevant. Obama hates it.
But we do expect better of a so-called Republican.