In early March I met with a dozen Republican U.S. senators for coffee as part of a series in which they invite writers, columnists and historians to share what’s on their mind. The consuming topic was the new president. I wrote some notes on the train down, seized by what I felt was the central challenge Republicans on Capitol Hill were facing. The meeting was off the record, but I think I can share what I said. I said the terrible irony of the 2016 campaign was that Donald Trump was the only one of the 17 GOP primary candidates who could have gone on to win the presidency. Only he had the uniqueness, the outside-the-box-ness to win. At the same time Mr. Trump was probably the only one of the 17 who would not be able to govern, for reasons of temperament, political inexperience and essential nature. It just wouldn’t work. The challenge for Republicans was to make legislative progress within that context.

It was my impression the senators were not fully receptive to my thought. Everyone was polite but things were subdued, and I wondered later if I’d gone too far, been too blunt, or was simply wrong. Maybe they knew things I didn’t. Since then I have spoken to a few who made it clear they saw things as I did, or had come to see them that way.

I jump now to the recent story involving Sen. Bob Corker, Republican of Tennessee and chairman of the Foreign Relations Committee. In August he said publicly that Mr. Trump had not yet demonstrated the “stability” and “competence” to be successful as president. Mr. Trump, in a series of tweets, mocked the senator, calling him gutless and “Liddle Bob Corker.” Mr. Corker tweeted in response: “It’s a shame the White House has become an adult day care center. Someone obviously missed their shift this morning.”

After that he turned serious, in an interview with Jonathan Martin of The New York Times.

Mr. Martin asked if Mr. Corker was trying to “sound some kind of alarm” about the president. Mr. Corker said “the president concerns me.” He likes him, it isn’t personal, but “I know for a fact that every single day at the White House it’s a situation of trying to contain him.” He said there are “some very good people” around the president, “and they have been able to push back against his worst instincts… . But the volatility is, to anyone who has been around, is to a degree alarming.” In particular, he observed: “The tweets, especially as it relates to foreign policy issues, I know have been very damaging to us.”

Mr. Martin asked if Mr. Corker has Senate colleagues who feel the same way. “Oh yeah. Are you kidding me? Oh yeah.”

Mr. Martin asked why they did not speak out. Mr. Corker didn’t know: “Look, except for a few people, the vast majority of our caucus understands what we’re dealing with here. There will be some — if you write that, I’m sure there will be some that say, ‘No, no, no I don’t believe that,’ but of course they understand the volatility that we are dealing with and the tremendous amount of work that it takes from people around him to keep him in the middle of the road.”

Among them are Defense Secretary Jim Mattis, Secretary of State Rex Tillerson and Chief of Staff John Kelly: “As long as there’s people like that around him who are able to talk him down, you know, when he gets spun up, you know, calm him down and continue to work with him before a decision is made. I think we’ll be fine.” He said of the president: “Sometimes I feel like he’s on a reality show of some kind, you know, when he’s talking about these big foreign policy issues. And, you know, he doesn’t realize that, you know, that we could be heading towards World War III with the kinds of comments that he’s making.”

This is all pretty striking from a sitting senator, even one not running for re-election.

At roughly the same time, some sharply critical pieces on the president were coming from the nation’s newspapers. The Los Angeles Times had a story on Mr. Trump’s reaction to Mr. Kelly’s efforts at imposing order on the White House: “The president by many accounts has bristled at the restrictions.” The article quotes allies of the president describing him as “increasingly unwilling to be managed, even just a little.” A person close to the White House claimed Messrs. Kelly and Trump had recently engaged in “shouting matches.” In The Washington Post, Anne Gearan described the president as “livid” this summer when discussing options for the Iran nuclear deal with advisers. He was “incensed” by the arguments of Mr. Tillerson and others.

Also in the Post, Michael Kranish interviewed Thomas Barrack Jr. , a billionaire real-estate developer and one of the president’s most loyal longtime friends. Mr. Barrack delicately praised the president as “shrewd” but said he was “shocked” and “stunned” by things the president has said in public and tweeted. “In my opinion, he’s better than this.”

Vanity Fair’s Gabe Sherman said he’d spoken to a half-dozen prominent Republicans and Trump associates, who all describe “a White House in crisis as advisers struggle to contain a president who seems to be increasingly unfocused and consumed by dark moods.” Mr. Sherman reported two senior Republican officials said Mr. Kelly is miserable in his job and is remaining out of a sense of duty, “to keep Trump from making some sort of disastrous decision.” An adviser said of Trump, “He’s lost a step.” Two sources told Mr. Sherman that several months ago, former chief strategist Steve Bannon warned the president the great risk to his presidency isn’t impeachment but the 25th Amendment, under which the Cabinet can vote to remove a president temporarily for being “unable to discharge the powers and duties of his office.”

There are a few things to say about all this. First, when a theme like this keeps coming up, something’s going on. A lot of people appear to be questioning in a new way, or at least talking about, the president’s judgment, maturity and emotional solidity. We’ll be hearing more about this subject, not less, as time goes by.

Mr. Corker deserves credit for going public with his reservations and warnings. The U.S. is in a challenging international environment; it’s not unfair or unjust to ask if the president is up to it and able to lead through it.

But we are a nation divided on the subject of Donald Trump, as on many others, and so this is a time to be extremely careful. Unnamed sources can — and will — say anything. If you work in the White House or the administration and see what Mr. Corker sees, and what unnamed sources say they see, this is the time to speak on the record, and take the credit or the blows.

What a delicate time this is. Half the country does not see what the journalists, establishment figures and elites of Washington see. But they do see it, and they believe they’re seeing clearly. It’s a little scary. More light is needed.

Reprinted by permission from peggynoonan.com.