Sen. Jeff Flake (R-AZ) on Tuesday took President Donald Trump to task for suggesting that Democrats in Congress were “un-American” and “treasonous” for not sufficiently clapping during his State of the Union address last week.

White House spokesperson Hogan Gidley said Tuesday that the remark was “tongue in cheek.” In press secretary Sarah Huckabee Sanders’ words, “He was clearly joking.”

Flake responded from the Senate Floor: “Treason is not a punchline, Mr. President.”

The senator announced in October that he would not seek re-election to his office, and since then he has been a reliably critical voice of the President’s habit of violating democratic norms (though Flake still votes with the President’s priorities the vast majority of the time).

Flake on Tuesday referenced the address he made upon announcing his retirement, saying, “I wish I could stand here today and say my words of last October have been proven wrong.”

He continued, “that I had been unfair to inveigh against the daily sundering of our country, that I had been mistaken about the personal attacks, that I had exaggerated the threats against principles, freedoms and institutions, the flagrant disregard for truth and decency, the reckless provocations most often for the pettiest and most personal reasons, reasons that have nothing whatsoever to do with the fortunes of the people that we have been all been elected to serve.”

“I wish I could say that I had been wrong, but I cannot,” he said.

Flake said it was “unconscionable” to suggest — as Trump did — that Democrats don’t love the country as much as Republicans.

“None of us in Congress pledge loyalty or service to the President,” he said. “This is not a royal court. Our oath is to the Constitution and to the people.”

“As members of Congress, we must never accept undignified discourse as normal because of the requirements of tribal party politics,” he continued. “None of this behavior should ever be regarded as normal. We must never allow ourselves to lapse into thinking that this is just the way things are now. We will get through this period, and when we do, we will look back at the destruction of our discourse and attacks on our democratic values as nothing but a tragedy.”

Flake concluded by urging colleagues to reject Trump’s “aberrant, destructive behavior.”

“And we must never shrink from opposing it,” he said, “for it is in the opposing this behavior that we defend our noms, our ideals and our values. It is in opposing this behavior that we stand for decency.”

Flake posted a clip of the speech to his Twitter account. Watch below: