"If I have been critical, it not because I relish criticizing the behavior of the President of the United States," Flake said. "If I have been critical, it is because I believe that it is my obligation to do so, as a matter of duty and conscience."

Republican Sen. Jeff Flake won't run for re-election

Washington (CNN)Republican Sen. Jeff Flake of Arizona, who has sparred frequently with President Donald Trump, will not run for re-election, he said Tuesday as part of a blistering floor speech bemoaning the changing tenor of politics in the United States.
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He continued, "The notion that one should stay silent as the norms and values that keep America strong are undermined and as the alliances and agreements that ensure the stability of the entire world are routinely threatened by the level of thought that goes into 140 characters -- the notion that one should say and do nothing in the face of such mercurial behavior is ahistoric and, I believe, profoundly misguided."

http://www.cnn.com/2017/10/24/politics/jeff-flake-retirement-arizona/index.html