'Donald who?' Presidential historian predicts GOP support for Trump will erode in the face of a 'blue wave'

MSNBC's Jon Meacham predicts that President Donald Trump won't be able to count on Republican support through a lengthy vote-counting process.

The historian and author told MSNBC's "Morning Joe" that GOP support may wane if Democrats strengthen their House majority and take over the Senate from Majority Leader Mitch McConnell, even if the results of the presidential election aren't known until weeks later.

"There's a much better chance that Joe Biden will end up somewhat centering the Democratic Party than anybody is going to come along and center the Republican Party," Meacham said, "and I think that's an existential threat to a Republican Party that has sold its soul, the check bounced, and they've got to figure out what are they going to do to attempt to be something approaching majority party in this demographically changing country."

Republican support for a highly divisive president could erode before the votes are counted, Meacham said, if the GOP suffers a blowout loss in congressional races.

"My bet is, sometime in the middle of November of this year, because it's going to take a while to count the ballots," Meacham said. "Let's not talk about Election Night, let's talk about election week, as people have been arguing. Let's not set up the expectation that we're going to know everything and David Brinkley is going to tell us everything at the right time because that plays into Trump's hand, chaos helps him. I think if there's a blue wave-ish, there's going to be a point before the end of the year where a lot of Republicans are going to say, 'Donald who? No, I don't know what you're talking about, I don't know who that is.'"

The president's flailing interview with Axios reporter Jonathan Swan has already helped set that dynamic in motion, Meacham said.

"If they do, it's because of that kind of clip," he said.