You are cleaning up Trump's comments after the fact. This is what he said:

"Ladies and gentlemen, I want to make a major announcement today: I would like to promise and pledge to all of my voters and supporters, and to all of the people of the United States, that I will totally accept the results of this great and historic presidential election – if I win." 

So what if he doesn't win? What will he do then?

Everybody knows Trump's a liar, and NOW everybody knows that you're a liar too.