WASHINGTON — Senator Jeff Flake, the Arizona Republican who has tangled with President Trump for months, announced on Tuesday that he would not seek re-election in 2018, declaring on the Senate floor that he “will no longer be complicit or silent” in the face of the president’s “reckless, outrageous and undignified” behavior.
Mr. Flake made his announcement in an extraordinary 17-minute speech in which he challenged not only the president but also his party’s leadership. He deplored the “casual undermining of our democratic ideals” and “the personal attacks, the threats against principles, freedoms and institutions, the flagrant disregard for truth and decency” that he said had become prevalent in American politics in the era of Mr. Trump.
The announcement appeared to signal a moment of decision for the Republican Party. Last week, Senator John McCain, the senior senator from Arizona, spoke in Philadelphia, denouncing the “half-baked, spurious nationalism” that he saw overtaking American politics. Former President George W. Bush, in yet another speech, lamented: “We’ve seen nationalism distorted into nativism.”
On Tuesday morning, Mr. Trump had renewed his attacks on another critic in the Republican Party, Senator Bob Corker of Tennessee, saying he “couldn’t get elected dog catcher in Tennessee.” Mr. Corker, appearing more weary than angry, said the president “is debasing our country.”
But Mr. Flake, choosing the Senate floor for his fierce denunciation of the president, appeared to issue a direct challenge to his colleagues and his party.
“It is often said that children are watching,” he said. “Well, they are. And what are we going to do about that? When the next generation asks us, ‘Why didn’t you do something? Why didn’t you speak up?’ What are we going to say?”
Without mentioning Mr. Trump by name, Mr. Flake, 54, took direct aim at the president’s policies, notably his isolationist tendencies, but also his behavior and that of his aides. In his time in Washington, Mr. Flake embodied an old-line conservatism. He avidly pitched smaller government, spending cuts and an end to home-district pork-barrel projects, but also supported free trade, engagement with the world and an openness to immigration.
Those positions stood in marked contrast to Mr. Trump’s inward-looking, anti-immigration nationalism. The senator had already touched on such themes in a book he published in August, “Conscience of a Conservative,” that was highly critical of the president. In his speech, he was at turns somber and passionate.
“We must stop pretending that the degradation of our politics and the conduct of some in our executive branch are normal,” Mr. Flake said. “They are not normal. Reckless, outrageous and undignified behavior has become excused and countenanced as telling it like it is when it is actually just reckless, outrageous and undignified. And when such behavior emanates from the top of our government, it is something else. It is dangerous to a democracy.”
As he spoke, Senator Mitch McConnell, the majority leader, Mr. McCain and Mr. Corker sat listening on the Senate floor. Mr. Corker had jousted with the president only hours before.
“Isn’t it sad that lightweight Senator Bob Corker, who couldn’t get re-elected in the Great State of Tennessee, will now fight Tax Cuts plus!” Mr. Trump wrote on Twitter on Tuesday morning, fearing that Mr. Corker’s vow to oppose any tax plan that increases the federal debt could imperil his tax push.
Mr. Corker snapped back, “Same untruths from an utterly untruthful president.”
“I don’t know why he lowers himself…