Sen. Jeff Flake, one of the most vocal critics of President Trump in the Republican Party, said Wednesday that Trump has “debased” the presidency and that the nation’s leadership “may have hit bottom.”

In an interview with The Washington Post and an address to the graduating class at Harvard Law School, the Arizona Republican offered a sharply critical view of Trump’s time in the White House and called on the next generation to chart a different course.

“Our presidency has been debased,” Flake said. “By a figure who has a seemingly bottomless appetite for destruction and division. And only a passing familiarity with how the Constitution works.”

He added: “Simply put: We may have hit bottom.”

Asked in the interview for examples of how Trump has debased the presidency, Flake singled out his name-calling.

“When you refer to your opponents in the legislature, for example, in the Congress, and call them losers and clowns and nicknames for people — that’s debasing the presidency. That’s not presidential,” he said.

A White House official did not immediately respond to a request for comment.

Flake is retiring from Congress this year. He has stood out from other leading figures in his party in his willingness to bluntly criticize the president publicly. His posture has stoked chatter about whether he might challenge Trump in the 2020 Republican presidential primary.

“There’s a lot of time between now and 2020,” Flake said in the interview. He said, though, his thinking hasn’t changed lately: “It’s not in my plans, but I’m not ruling anything out.”

He added: “I do hope that somebody challenges the president in the primary — if only to remind Republicans what Republicans stand for.”

Flake said he hoped that more Republicans will stand up to Trump.

“I am concerned that we are sounding too much like the president’s Cabinet. And we’re not,” he said.