I think Donald Trump has come to that realization. Which is why he's been so confident the past few days. If he wasn't, he would have waited for the press to arrive before speaking in NH Thursday night and he certainly wouldn't have done what he did to the press at his new hotel in Washington DC yesterday. Also, he was completely at ease in his appearance on Jimmy Fallon the other night. Otherwise he would not have allowed Fallon to mess up his hair.
I'm sure Kellyanne and others around him caution him, but he's going to follow his intuition, wherever that goes. He seems very confident about the first debate, he's mentioned looking forward to it. Hillary is going to come off as wooden, scripted, phony. The public isn't going to judge that debate over who is the better wonk.
I think his confidence comes from the poll direction - he needs to be careful because those numbers are still, this far out, at the whim of the press.