Arizona Senator Jeff Flake, an old-school conservative Republican who rejects Donald Trump’s remodeling of the Republican Party as a dangerously destructive cult of personality, announced Tuesday that he would not seek reelection to a Republican-controlled Senate that more frequently than not serves as a rubber stamp for Trump and Trumpism.

The maverick senator, who had been targeted for defeat in the 2018 Arizona Republican primary by the president’s political henchmen (most notably former White House chief strategist Steve Bannon), did not mention Trump by name in his emotional address to the Senate. But there could be no mistaking Flake’s message to his stunned colleagues and to his country.

“Reckless, outrageous and undignified behavior has become excused as telling it like it is when it is actually just reckless, outrageous and undignified,” Flake declared. “And when such behavior emanates from the top of our government, it is something else. It is dangerous to a democracy.”

Flake addressed much of his speech to his fellow Republicans, whose complicity with Trump he warned is transforming the GOP into a “fearful, backward-looking minority party.”

I rise today with no small measure of regret. Regret, because of the state of our disunion, regret because of the disrepair and destructiveness of our politics, regret because of the indecency of our discourse, regret because of the coarseness of our leadership, regret for the compromise of our moral authority, and by our—all of our—complicity in this alarming and dangerous state of affairs, It is time for our complicity and our accommodation of the unacceptable to end.

Flake acknowledged that his brand of conservatism-with-conscience, which owes more to Republicans such as Robert Taft and Barry Goldwater than to the likes of Mitch McConnell and Paul Ryan, has been sidelined in Trump’s Grand New Party. The senator explained,

It is clear at this moment that a traditional conservative who believes in limited government and free markets, who is devoted to free trade, and who is pro-immigration, has a narrower and narrower path to nomination in the Republican party—the party that for so long has defined itself by belief in those things.

It is also clear to me for the moment we have given in or given up on those core principles in favor of the more viscerally satisfying anger and resentment. To be clear, the anger and resentment that the people feel at the royal mess we have created are justified. But anger and resentment are not a governing philosophy.

Flake also acknowledged that he was challenging a basic premise of the hyper-cynical Republican Party that has been forged by Ryan, McConnell, and other apologists for the 45th president: that partisanship trumps principle. “I am aware,” he said, ”that a segment of my party believes that anything short of complete and unquestioning loyalty to a president who belongs to my party is unacceptable and suspect.”

There can be no doubt that it was Flake’s hope that he could shake his colleagues out of their partisan stupor. “If I have been critical, it not because I relish criticizing the behavior of the president of the United States,” he 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. 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.

The senator’s sentiments were correct.

But they were not respected.

When McConnell and Arizona Senator John McCain came to the Senate floor immediately following Flake’s dramatic address, they praised the retiring senator in effusive terms. They did not, however, answer his call for Republicans to end their complicity with Trump.

The words spoken by McConnell and McCain were warm and pleasant, but wholly inconsequential.

While a few Republican senators, such as Nebraska’s Ben Sasse, may be counted on Flake’s side of the conscience divide, most Republicans will stand with the man in the White House. They will continue to enable Trump and advance a presidential program that largely mirrors their own rigidly right-wing agendas—even if they may grumble privately about cruel and unusual tweets.

The measure of responsible Republicanism in these times cannot be made with words—not even with words so powerful as those employed by Jeff Flake on Tuesday afternoon. Deeds are required. It is not enough to suggest, as Flake and Senate Foreign Relations Committee chairman Bob Corker have, that Trump is unfit for office.

If this president is dangerous, then Flake, Corker, and their colleagues should move to disempower him. They should support the efforts of Senator Ed Markey (D-MA) to signal that the president does not have the authority to order the first-strike use of nuclear weapons. They should address the ethical abuses of this president with motions to censure him. And they should encourage Republican members of the House to align with the Democrats who have begun an appropriate and necessary outlining of articles of impeachment.

If a president is dangerous, he should not merely be identified as such. He should be checked and balanced by Congress.

Unfortunately, Trump can only be checked and balanced in this moment of Republican congressional hegemony if members of his own party recognize that they owe a greater duty to the Constitution than to a billionaire brigand who has commandeered the “Party of Lincoln” and made it his own.

Most Republicans in Congress still do not recognize that greater duty. No call to conscience will sway them. They are consciously complicit, as Tuesday’s rote remarks by McConnell and McCain so painfully illustrated.