From MSNBC's October 19 post-debate coverage:
MICHEAL BESCHLOSS: For starters Mike Pence, I think six months ago, we would have thought that if a presidential nominee like Donald Trump had said such a thing in a debate of as we heard tonight which is astounding and for all we have discussed tonight, fifty years from now historians will remember this debate for exactly one thing and that is Trump refusing to say that he'll accept the results of the election. You would have thought every value we know of Mike Pence, he would have been first to say that Donald Trump did the wrong thing tonight and you sort of wonder to what length he will go to justify the top man on his ticket. Especially because just the other day Pence said Mr. Trump will accept the results of the election. It really astounding. But really in a large sense everything you and Rachel have said about this is -- I mean I would even go further. I think it is radical. I think it is revolutionary.
I think this was a deliberate threat he made tonight and it really is out of keeping with American history. Because one of the few things that everyone agreed on all the way back to George Washington is that no matter how tough a campaign is, how close it is, we all accept the results, even Richard Nixon, 1960 3:15 AM when he made a tentative concession to John Kennedy he said “One of the great features of American democracy is that once the decision is made, we unite behind the person of the person that's elected.” And so once again we've seen a lot of things unprecedented this year but that's another precedent Donald Trump tonight has thrown on his head and that's absolutely horrifying.