Senate Foreign Relations Chairman Bob Corker on Thursday lambasted Donald Trump, saying the president is driving the United States toward “great peril” because he lacks the “stability” and “competence” for the country’s highest office.

The Tennessee Republican once appeared on stage at a Trump campaign rally, but it any goodwill he might have built with Trump likely evaporated Thursday. The president, as he did with a Twitter attack earlier in the day on Sen. Lindsey Graham, R-S.C., often attacks any critics — and holds grudges.

“The president has not yet been able to demonstrate the stability nor some of the competence that he needs to demonstrate in order to be successful,” Corker said during an interview that was posted on Facebook.

“He also, recently, has not demonstrated that he understands the character of this nation,” Corker added, apparently referring to the recent racially tinged violence in Charlottesville, Va. “He has not demonstrated that he understands what has made this nation great and what it is today. … And without the things that I just mentioned happening, our nation is going to go through great peril.”

Corker once was considered a candidate for secretary of state — even vice president — under Trump. But on Thursday, he said Trump must find “way more discipline” and “a lot more inner strength” in order to “be measured and to try to solve problems.”