Arizona GOP Sen. Jeff Flake quits with attack on Trump

Arizona Republican Senator Jeff Flake, in a surprise announcement, confirmed on Tuesday that he will not run for re-election in 2018, citing the Republican Party's changing tide toward U.S. President Donald Trump.

He also took a parting shot on the Senate floor at President Trump for the behaviour he called "reckless, outrageous, and undignified", reports Fox News.

Without mentioning the President by name, Flake accused the Republican Party of having "given in or given up on the core principles in favour of a more viscerally satisfying anger and resentment ... but anger and resentment are not a governing philosophy."

"None of these appalling features of our current politics should ever be regarded as normal," Flake said in a fiery speech on the Senate floor, just hours after Trump had left the Capitol. "We must never allow ourselves to lapse into thinking that is just the way things are now. If we simply become inured to this condition, thinking that it's just politics as usual, then heaven help us."

"The notion that one should stay silent as the norms and values that keep America strong are undermined," Flake added, "and as the alliances and agreements that ensure the stability of the entire would are routinely threatened by the level of thought that goes into 140 characters ... is ahistoric and, I believe, profoundly misguided."

Flake's speech was greeted with applause in the Senate chamber.

Meanwhile, President Trump's eldest son, Donald Jr., tweeted a link to an Arizona Republic story announcing Flake would not run for re-election with the hashtag "#MAGA."

Flake has had a tumultuous relationship with the Trump administration.

In August, he criticised the President's immigration policy, to which the latter tweeted that Flake was "WEAK on borders, crime and a non-factor in the Senate."

The 54-yeard-old American politician was elected to the Senate in 2012, after 12 years in the House of Representatives.