The national media, and especially ABC News, is thoroughly bludgeoning Donald Trump on a daily basis. I think this is the only reason he trails in the polls right now. Its going to take something tremendous for Trump to close the gap and move ahead. Unless a massive outpouring of voters show up at the polls to support him. He actually has 2 enemies. The media and the establishment republicans, who are making it tough to sway enough of the Rubio, Cruz, and Kasich supporters.
It is true that the media can do an excellent job of shaming people into not wanting to admit that they want to vote for him and this may be what is hurting him in the polls.