No one would commit beforehand to accept results before they know how those results were arrived at, especially if they think fraud will be occurring. If he said "I'll accept the results" and then something happens and he objects the same jokers would be saying "he lied about accepting results." The whole point of the question was to attempt to tie his hands no matter how he answered.
Trump was questioning election integrity even in 2012 in tweets. I don't know if it goes before that.
Blocked either for having no sense of humor to be able to detect an obvious as hell joke intended for his audience or for being disingenuous as hell.Here is another video in 2016 where he says he will only accept the result if he wins:
Trump: I will accept election results ... if I win - YouTube