“Sustained incumbency is not the point of seeking office, and there are times when we must risk our careers in favor of our principles,” said Republican Sen. Jeff Flake, of Arizona, in a searing speech.

If only that’s what Flake was doing.

Flake’s speech on the floor of the Senate on Tuesday will prove a historic document in American politics. It is an explosive denunciation of the president of the United States, and of his Republican enablers. Flake has long been critical of President Trump, but he has never made his case so starkly, nor condemned his fellow Republicans for their silence and cowardice so clearly.

But in choosing to retire rather than run for reelection, Flake is sending the worst possible message to his colleagues, empowering the president he loathes, and accelerating the takeover of the Republican Party that he laments.

America does not need Flake’s courageous retirement. It needs his courageous reelection campaign.

“It is often said that children are watching. Well, they are.”

Flake’s speech is worth reading in full, but a few particular quotes are worth pulling out:

“It is often said that children are watching. 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? Mr. President, I rise today to say, enough. We must dedicate ourselves to making sure that the anomalous never becomes the normal.”

“Were the shoe on the other foot, would we Republicans meekly accept such display from dominant Democrats? Of course we wouldn't, and we would be wrong if we did.”

“When we remain silent and fail to act when we know that silence and inaction is the wrong thing to do, because of political considerations, because we might make enemies, because we might alienate the base, because we might provoke a primary challenge, because ad infinitum, ad nauseam, when we succumb to those considerations in spite of what should be greater considerations and imperatives in defense of our institutions and our liberty, we dishonor our principles and forsake our obligations.”

“None of this is normal. And what do we, as United States senators, have to say about it? The principles that underlie our politics, the values of our founding, are too vital to our identity and to our survival to allow them to be compromised by the requirements of politics. Because politics can make us silent when we should speak, and silence can equal complicity. ”

But here, at the end, was Flake’s confounding conclusion: “I will not be complicit or silent. I've decided that I would be better represent the people of Arizona and to better serve my country and my conscience by freeing myself of the political consideration that consumed far too much bandwidth and would cause me to compromise far too many principles. To that end, I'm announcing today that my service in the Senate will conclude at the end of my term in early January 2019.”

Parties are won and lost in elections, and Flake is abandoning that fight

Flake’s decision to retire so he can speak his mind is certainly preferable to choosing to seek reelection while remaining silent. But these are extraordinary times, and they demand more than retirement. Perhaps Flake would have lost reelection if he ran in a Republican primary on the principles and moral behavior he believes in. Perhaps he would have lost if he had mounted an independent candidacy on the principles and moral behavior he believes in. But maybe he would have won, and if he did win, he would have emboldened others in his party, and outside his party, to follow his example.

Three Republican senators have now reoriented themselves to forcefully oppose Trump. Flake is one. Tennessee’s Bob Corker, who also announced his retirement, is another. And Flake’s Arizona colleague, John McCain, who is facing brain cancer, is a third. It is no accident that the three Republicans who are speaking their minds about Trump are the three who have nothing left to fear from the Republican base. But it is a shame.

The souls of political parties are won and lost in elections. For the Republican Party to be recaptured by candidates like Flake and Corker requires candidates like Flake and Corker to face down the Trumpist faction of their base and win. That is the only way their colleagues will learn that the Trumpist faction of their base can be beaten.

“It is clear at this moment that a traditional conservative ... has a narrower and narrower path to nomination in the Republican Party,” Flake says, and he is likely right. His reelection campaign was endangered at best. But to proclaim the job impossible and retire in expectation of a loss is to say that the only Republicans who can speak out against Trump are those who have abandoned any hope of a political future. That is a price most Republican politicians will not pay, and so it is among the most damaging of messages that can possibly be sent.

Nor is it the case that losing a party primary necessarily means losing the election. Just in the past few years, both Joe Lieberman and Lisa Murkowski have lost primary bids only to win reelection to the Senate as independents. Flake could have attempted a similar path.

And if Flake ran and lost, so be it. Then he would have at least proven that the Republican Party is what we fear it is, and that an alternative is needed. But to simply resign from the fight is to do less than he is asking of his colleagues, and of the rest of us.