Senator Jeff Flake earned the media spotlight last week after delivering a scathing speech against President Donald Trump. He also announced his decision not to seek re-election after his term.

In his speech, Flake highlighted the destructiveness of the U.S. politics, indecency of discourse, and coarseness of its leadership. He said the American democracy is now defined by its leaders’ political discord and dysfunction.

The senator also emphasized that it is his “obligation” to be critical of Trump as a “matter of duty and conscience.” Flake said he does not want to be complicit.

In a recent interview with The Washington Post, Flake said his decision was driven by his disgust with Trump’s behavior.

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

Flake condemned Trump/GOP in his book

The Arizona senator is among the Republicans who have been vocal in criticizing Trump. Flake refused to endorse the real estate mogul during his presidential campaign. He also wrote a book entitled “Conscience of a Conservative” criticized not just Trump but also some Republicans. He condemned those Republicans turning a blind eye and making a “Faustian bargain” when Trump forsake GOP’s core conservative principles.

Flake wrote that Republicans gave in to the “politics of anger.” They embraced the “belief that riling its base can make up for failed attempts to broaden the electorate.” He said, “These are the spasms of a dying party."

He told the Washington Post that he was compelled to criticize Trump in the press and in his book. Flake said he was repeatedly disgusted by the President’s distasteful behavior.

Flake knew many Republican primary voters do not agree with him

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

Based on polling data, Flake is unlikely to win the Republican primary next year. His challenger is former State Senator Kelli Ward, strong supporter of Trump. Former White House chief strategist Steve Bannon, who declared a war against GOP incumbents, is supporting Ward’s senate bid.