WATCH: John Heilemann Explains Thing He Believes to Be "The Trumpiest Thing Ever"

During a discussion before tonight's debate, John Heilemann explained how Donald Trump's slams on Kamala Harris before the debate were a really bad decision. 

Common knowledge in Washington, D.C., says that you should always shine your opponent up a bit before a debate. If you then lose the debate, you lose to a powerful opponent. But if you win, you were able to defeat a terrific foe. 

Although Donald Trump was undoubtedly informed of this, he did the opposite. According to Trump and his people, Harris is so dumb that he won't be able to hide his disdain. 

When discussing Trump's tactics with Nicolle Wallace, Heilemann opined, "Any of the candidates that we've covered, every one of them has tried to spin expectation before a debate. How do you do that? How they always do it. My rival, my opponent, is so good as a debater, is so brilliant, is so strong I will be lucky if I survive this debate, right? Lowering expectations for yourself."

The pundit continued, "I mean, really, I've never seen anything like that before, but it is so Trumpy. It just blows my mind."

The host then chimed in, "I think some of it might be in the eye of the beholder because I saw it when they were talking about him like he was an untrained male puppy who couldn't help but pee on the fire hydrant."