Stick a fork in him, he's done.
When the one takeaway from the debate that you give people is that you refuse to state that you will accept the outcome of the election if you lose, no one is going to remember anything else that was said in the debate.
It is truly horrifying that a presidential candidate dares to undermine the legitimacy of our electoral process AHEAD OF TIME. Heck, even Al Gore conceded once the legal challenges to the recounting process were exhausted:
"Let there be no doubt, while I strongly disagree with the court's decision, I accept it. I accept the finality of this outcome which will be ratified next Monday in the Electoral College. And tonight, for the sake of our unity as a people and the strength of our democracy, I offer my concession. I also accept my responsibility, which I will discharge unconditionally, to honor the new President-elect and do everything possible to help him bring Americans together in fulfillment of the great vision that our Declaration of Independence defines and that our Constitution affirms and defends." - Al GoreAnd this doesn't even take into account his lying to the moderator, his "No, you are!" whine worthy of a six-year-old, or Clinton's masterful defense of her decades in politics, as compared to his shady career in real estate and self-promoting career in entertainment.
He's toast, and he knows it. And no badly hacked-together "video" or WikiLeak of e-mails and documents showing a politician and her staff doing the necessarily difficult and complex business of politics is going to change that.
He took a chance at applying for a job that was way beyond him. Somehow, he made it to the interview stage. Instead of being thankful for the opportunity and cramming as much as possible on the nature of the job he wanted, he thought that simply wearing clean collars and a brand new suit to the interviews would have been enough preparation.
Naturally, he got taken to the cleaners by someone who has forgotten more about government then he will ever learn. He's reduced to whining and sulking and ripping up his notes in a hissy fit.
He's sunk so low he's even getting booed at a charity dinner:
http://www.usatoday.com/story/news/politics/onpolitics/2016/10/20/al-smith-dinner-reactions/92493992/What's really worrisome is not him refusing to go quietly, but that some of his more rabid followers will commit violence in response when he loses..... And it will be his fault for allowing if not encouraging them.