“I knew that when I spoke out at that time that I was out of step with a lot of the Republican primary voters, but I felt that I had to do it,” he said in an interview. “I had hoped — and I still hope and I’m confident at some point — that the fever will break. But it just became more and more apparent that it certainly wasn’t going to break by next year.”

Even if he survived the primary, neither Flake nor others in his orbit deny that the same polling showed he might also have lost the general election to his presumed Democratic opponent, popular Phoenix-area congresswoman Kyrsten Sinema.

But it was his disgust with Trump’s behavior that proved decisive in his decision to call it quits.

“I couldn’t sleep at night having to embrace the president or condoning his behavior or being okay with some of his positions,” he said. “I just couldn’t do it — it was never in the cards.”