UDPATED with video: MSNBC morning show host Joe Scarborough told Late Show host Stephen Colbert he’s having trouble transitioning from calling POTUS “Donald” to “Mr. President.”

“I’ll be really honest with you; the way he’s acted over the past month has made it even harder to call him Mr. President,” Scarborough said, noting, disapprovingly, that Trump has questioned judicial review and the legitimacy of a federal judge.

Republicans in the Senate, in particular, need to stand up and say “this is not right.”

“The Republican Party needs to know there is going to be a time after Donald Trump, and they’re going to be judged for the next 50 years on how they respond to the challenges today,” Scarborough explained.

“I wish I shared your optimism that there will be a time after Donald Trump,” Colbert snarked back, wondering if Scarborough thought the “fever pitch” of Trump’s first month is a “sustainable atmosphere” for four years.

“Republicans and Democrats alike all agree this pace can’t be sustained,” Scarborough acknowledged. “I don’t think it will last four years.”

“I think we’ve already died a million deaths the first month,” he added.

Republicans are telling him “they’re very worried about how erratic [Trump has] been,” the cable news host said. “Of course they’d like to pass tax cuts, like to pass regulatory reform. They’d like to have their own health care reform plan out there, but they’re concerned.”

The gravity of the situation hit Scarborough, he said, this past weekend when Trump called the press the enemy of the American people. In response, Sen. Ben Sasse, a Republican from Nebraska who has spoken out against Trump, tweeted the text of the First Amendment.

“I was excited and I retweeted it,” Scarborough said. “In 2017 it seems a subversive act to simply tweet the words of the First Amendment. That tells you where we are right now.”