On Thursday, the candidate challenging Speaker Paul Ryan in a Wisconsin Republican primary, Paul Nehlen, declared in a radio interview that the United States should consider deporting all Muslims. “I'm suggesting we have a discussion about it, that's for sure,” he said. “I am absolutely suggesting we figure out—here's what we should be doing. We should be monitoring every mosque. We should be monitoring social media. We've got about three million Muslims in the United States."

The comments came days after Donald Trump injected energy into his campaign by pointedly complimenting him on social media and refusing to endorse Ryan.

Meanwhile, down in Louisiana, David Duke, the former Klansmen who waged a losing campaign for governor in 1991, announced a return to electoral politics. “It would be hard to overstate how much former KKK leader David Duke has attempted to link his 2016 surprise Senate bid to that of the Republican presidential nominee,” the New York Daily News reports. “He mentioned Trump during a YouTube announcement of his bid and spoke repeatedly during an hour-long news conference about how Trump and the Republicans had embraced his vision of America. References to Trump now compete for attention on Duke's website with anti-Zionist posts like the theory that Jewish conspirators somehow worked passages from a Michelle Obama speech into Melania Trump's convention address.”

This is the GOP’s future if Donald Trump wins.

In Republican primaries, opportunists will try to mimic Trump’s ugly brand of identity politics and actual white nationalists will be emboldened to vie for power in the GOP. They will win in some regions and transform the tenor of local politics in many more, alienating a broad swath of Americans on the right and the left. If you don’t believe me look at how people already behave at Donald Trump rallies.

That faction may become the bane of all other Republicans.

The trajectory would do great harm to the conservative movement and the progressive left, so much so that it’s in their mutual interest to cooperate to stop it.  If Trump fails––especially if he loses in a humiliating landslide––the defeat will go a long way toward discrediting that same brand of right-wing identity politics, putting the GOP on a trajectory that would benefit conservatives and progressives alike.

It would, however, benefit them in different ways.

Why Conservatives Should Fear White Identity Politics

The self-interested reason for conservatives to fear white identity politics is demographic: there’s an expiration date on any coalition that wins white men without college degrees but alienates a “Rainbow coalition” that includes college-educated whites. That date may have already passed. Imagine choosing now, of all moments, to run a campaign that actively antagonizes Hispanics who were born in the United States.

Regardless, it dooms movement conservatism in the long term.

And even if Trump wins this year, there is reason for conservatives to fear the identity politics he embodies and inspires even in the short term. That is partly because he will embrace redistributionist big government, albeit an iteration that directs its spoils to different constituencies. His efforts will displace much of what existing factions in the GOP hold dear: Neither social conservatives nor libertarian-leaning Republicans nor neoconservatives will gain standing. All may lose it.

The cultural debate about political correctness will be transformed as the face of what’s “politically incorrect” changes from, say, a college professor embroiled in a Kafkaesque “bias investigation” for failing to issue a “trigger warning,” to a xenophobic demagogue insulting the parents of a fallen Muslim American soldier.

And as Republican governors in blue states and representatives in purple districts find themselves having to distance themselves from Trump’s agenda to retain their seats, the president himself will have a greater incentive to pander to his base—that is, the part of the GOP coalition that is least motivated by principled conservatism and most motivated by racism, xenophobia, and economic protectionism.

Why ‘Bernie-or-Busters’ Should Go All In Against Donald Trump

If a Donald Trump victory would do so much harm the to conservative movement, why would it be in the interest of progressives—especially progressives with an intense dislike of Hillary Clinton—to work to oppose that outcome?

One reason is the substantive damage Trump’s agenda will do in the short term. He will have every incentive to aggressively target millions of people in the United States with deportation. He poses a grave threat to the civil liberties of Muslim Americans, which would almost certainly suffer during his tenure, especially after a terrorist attack. And his Department of Justice will almost certainly abandon its current, already inadequate efforts to ensure that the equal protection of the law extends to African Americans and Hispanics in municipalities rife with law-enforcement abuses.

To declare as a progressive that there is no significant difference between Clinton and Trump is to assign a value of zero to the liberties of Hispanics, Muslims, and many blacks.

And the case for working to defeat Trump hardly ends there.

Insofar as the Republican Party becomes a ressentiment-driven coalition of white identity politics, Democratic candidates will have every incentive to campaign against it as Hillary Clinton has: by emphasizing the inclusiveness of the Democratic Party, its rejection of racial, ethnic, and religious bigotry, its embrace of women’s rights, and its sound long-term strategy of betting on a Rainbow coalition.

For Bernie-Sanders-inclined millenials, who believe that class rather than identity should be at the center of leftist politics, this trajectory will bring years of frustration. In contrast, a sufficiently decisive Trump defeat will cause Republicans to see their flirtation with white identity politics an abject failure, to cease alienating voters of color, and to formulate policies that appeal to non-white voters.

In turn, the Democrats will no longer be able to assure themselves of a strong performance merely by pointing at the cartoonish bigotry manifesting itself in the opposing party.

Consider two different scenarios.

In scenario one, Hillary Clinton barely beats Donald Trump. Some in the GOP conclude that his appeal to white identity politics could be successful if only it were executed better. They double down on scapegoating Hispanics and Muslim Americans. And Clinton’s reelection campaign looks a lot like her effort does this year.

In scenario two, Hillary Clinton routs Donald Trump. There is a broad realization in the Republican Party that white identity politics is a doomed strategy. It recasts its efforts by trying to win working class voters irrespective of race, courting young Hispanic families and working class whites alike with an agenda something like Ross Douthat and Reihan Salam laid out in Grand New Party. In that world, Hillary Clinton would be unable to lean as heavily on identity in her reelection effort. To avoid a primary challenge or a loss in the general election, she would have to advocate economic reforms and relief of a sort that Bernie Sanders would advocate.

A Final, Temporary Convergence

Beyond the distinct reasons that movement conservatives and Bernie Sanders progressives have for joining forces to stop a future where American politics pits two strains of ethnic identity politics against one another, there is a larger reason to oppose Trump: beyond policy, ideology, and political implications, he is unfit for office.

Although Trump voters don’t see it, every American has an interest in his defeat simply because he is an erratic, egomaniacal sociopath who lacks the experience, temperament, self-discipline, character, and decency to be president. On many occasions in the past, I’ve criticized Hillary Clinton, whose nomination I very much opposed. I don’t think she will make a good president. And yet, more than any election during my lifetime, deciding which of the two major party candidates is worse has never been clearer, because Trump is so abnormally unstable and dangerous.

Even as a fan of divided government who would prefer a Hillary Clinton administration to be checked by a skeptical Congress, I am rooting for a historic, landslide defeat of Trump this November, not just to stop the man himself, as vital as that is, but to forever discredit the poisonous brand of politics he threatens to bring into the mainstream.