WASHINGTON  — Sen. Bob Corker is hardly the only Republican leader lambasting Donald Trump and raising dark concerns about harm the president might cause the U.S. and the world.

“Cool it,” Sen. Chuck Grassley said in Iowa on Monday, delivering a message to both men. “And I think it would help if the president would be the first to cool it.”

Tennessee Sen. Corker, with his Twitter broadsides and his explosive weekend New York Times interview — he charged that Trump could set the nation “on the path to World War III” — gave voice to concerns that circulate widely on Capitol Hill about an unpredictable president whose tendency to personalize every issue creates risks for the nation.

But Trump’s enduring popularity with a segment of the GOP base serves as a political muzzle that keeps most elected Republicans from saying anything similar, even those who believe it to be true.

Grassley, who wouldn’t be up for re-election until 2022, responded bluntly when asked about the situation.

“I don’t see how it’s productive, and I think that two words would kind of answer your question from my point of view: Cool it … I think it would be better if we stuck to the issues and leave personalities out of it.”

A few other Republican senators who provided public views on Monday aligned themselves with Trump, not Corker.

For example, Montana’s Steve Daines’ office said simply that the senator “has confidence in the president.”

GOP Sen. John Barrasso disagrees with Corker, according to his office. Referring to Barrasso and Trump, the Wyoming senator’s office said, “On tax cuts, border security, and rebuilding American infrastructure, they fight the same fight.”

Barrasso is among the establishment Republicans who face potential primary challenges from pro-Trump activists on the right, heightening the political dangers if they should break with the president.

Corker offered no solution to the problem he identified so graphically. Trump is the president, and few doubt that he will remain so, despite constitutional provisions for impeachment or for the vice president to take over if the commander in chief cannot discharge his duties,

Moreover, Republicans’ political fortunes remain tied to the president’s. They need his signature if they are to rescue a flagging agenda and pass a tax overhaul, a goal many believe is imperative if the GOP is to retain control of Congress in next year’s midterm elections.