Sen. John McCain John Sidney McCainCindy McCain endorses Biden: He's only candidate 'who stands up for our values' Biden says Cindy McCain will endorse him Biden's six best bets in 2016 Trump states MORE's (R-Ariz.) former presidential campaign manager, Steve Schmidt, said early Thursday that President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE was "clearly slurring his words" during an announcement that the U.S. will recognize Jerusalem as the Israeli capital, adding that "the impairment is chilling."

"I don’t know the cause of it, but when you combine it with [Sen.] Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE’s critique that the president of the United States is unstable, that he’s dangerous, when you look at the private comments that are made by members of Congress around his stability, you look at his actions in recent weeks," said Schmidt, who is also an MSNBC contributor, on MSNBC's "Morning Joe."

ADVERTISEMENT

"The question of his fitness, of his stability, is in the air," Schmidt later added. "And it doesn’t get better when you see clear impairments."

Trump on Wednesday announced the U.S. will recognize Jerusalem as its capital and will move the U.S. Embassy there from Tel Aviv, keeping a campaign promise made in 2016.

The president appeared to have an issue with his speech toward the end of the announcement. Some in the media and many on social media speculated that he wears dentures and they were falling out, affecting his speech.

"#DentureDonald" was trending on Twitter for most of Wednesday into Thursday.

A White House spokesman, however, attributed Trump's slurred speech to "dry throat."

"I don’t know. Is that a tooth problem? Is that something else?" Schmidt asked on Thursday. "Presidents every year typically go to the Bethesda naval hospital for a checkup. This president, to my knowledge, is departing from that. We don't have updates on his health. We don’t know what’s going on, but this is a legitimate issue worthy of consideration. This is the man who commands America’s nuclear arsenal. And that video, that speech, that impairment, is chilling."

"Morning Joe" co-host Joe Scarborough has questioned Trump's mental fitness on several occasions in the past, with the former GOP congressman most recently stating on Nov. 30 that “people close to him during the campaign" told him "he had early stages of dementia."

Trump has not appeared on the MSNBC morning program or the network in any capacity since May 2016.

This report was updated at 9:40 a.m.