On July 31, the American Enterprise Institute (AEI) and the Center for American Progress (CAP) issued the second of two joint reports focusing on what they describe as “President Donald Trump’s assault on Europe” and “the current populist backlash against international cooperation, multilateralism, and the transatlantic alliance.”

For those lucky enough to be unfamiliar with the topography of Washington, DC’s small but influential universe of think tanks, the teaming up of AEI and CAP is noteworthy. After all, AEI has long served as the Beltway’s home to some of the leading lights of the neoconservative movement, while CAP is resolutely Clintonian in its policy preferences. Founded by longtime Democratic lobbyist John Podesta and run by former Hillary Clinton aide Neera Tanden, CAP sponsors the liberal-leaning Think Progress blog, among other projects.

But the CAP/AEI alliance is just the latest example of liberal Democrats’ teaming up with neocon hard-liners. Another widely remarked-upon merger was unveiled in July of 2017, when the German Marshall Fund of the United States launched its Alliance for Securing Democracy (ASD), which brought together Laura Rosenberger (an Obama and Clinton foreign-policy aide) and neoconservative think-tank operative and former Marco Rubio adviser Jamie Fly. The advisory council of the ASD pairs neocons like Bill Kristol and former John McCain aide David Kramer with liberal hawks like Podesta and former Clinton campaign advisers Jake Sullivan and former ambassador Michael McFaul.

In addition to the goings-on in think-tank land, a second manifestation of the alliance between neocons and mainstream liberal Democrats can be found in the elite media. Hard-line neocons Bret Stephens and Bari Weiss have been given real estate on the op-ed page of The New York Times; neocon publicist Max Boot was given a column at The Washington Post; Bill Kristol, David Frum, and Jennifer Rubin are frequently featured as guests on the liberal cable-news outlet MSNBC. Indeed, one need only survey the coverage of Senator John McCain’s days-long funeral to see just how strongly inculcated the neoconservative worldview has become among purportedly mainstream liberals like CNN’s Jake Tapper.

In a way, the alliance between neocons and mainstream liberals is, in this, the Age of Trump, less surprising than it first might appear. It actually began to manifest itself during the course of the 2016 election, when longtime neocons such as the Brookings Institution’s Robert Kagan and Max Boot publicly abandoned the GOP in favor of Mrs. Clinton. As I warned in The Nation at the time, “The danger in Kagan and Boot’s professed support for Hillary Clinton is this: Should even a few influential neocons return to their party of origin, the marginalization of progressive-realist foreign-policy voices within the Democratic Party would continue apace.”

There can be little doubt that the biggest boon to the fortunes of the neocons was the 2016 election, which in itself is richly ironic given that the neocons cheered on the Tea Party, which helped elect the beast that is Donald Trump. But now the neocons are at pains to disavow what the Tea Party has wrought. And prominent liberal institutions and media outlets are helping them to do so. In other words: Thanks to the mainstream liberal media, the neocon rehabilitation project is going strong.

And that is a problem.

It would be one thing if neocon intellectuals ever tried to come to an honest reckoning with their record. But they’ve never undertaken such an effort. In fact, as recently as 2015, Bill Kristol took to the pages of USA Today to declare not only that “we were right to invade Iraq in 2003,” but that the Bush administration was also “right to persevere” and “bring the war to a reasonably successful conclusion in 2008.”

As Harvard’s Stephen Walt has wryly observed, “being a neocon means never having to say you’re sorry.”

In a more sensible, less agitated time, given neoconservatives’ record and their utter lack of remorse for the multiple wars of choice that they helped to bring about, their worldview would be seen for what it is: morally obtuse and objectively wrong.

Putting aside the ethics of making common cause with people such as Kristol, there is also a practical reason for Democrats to shun the neocons: Their positions are deeply unpopular. A poll released earlier this year by J. Wallin Opinion Research showed that 86.4 percent of those surveyed feel the US military should be used only as a last resort, 57 percent feel that US military aid to foreign countries is counterproductive, and 70.8 percent said Congress should pass legislation to restrain military action overseas.

What some might excuse or justify as a “popular front” between liberal Democrats and neocons in the age of Trump is clearly problematic.

For one thing: We’ve seen this kind of so-called popular front before. During the run-up to the Iraq War, liberals like Paul Berman, Kenneth Pollack, David Remnick, Nicholas Kristof, Richard Cohen, and Jacob Weisberg lent their voices in the service of the Bush administration’s crusade to remake the Greater Middle East. At the time, the historian Tony Judt observed that George W. Bush’s liberal supporters, “long nostalgic for the comforting verities of a simpler time,” have “at last discovered a sense of purpose: they are at war with ‘Islamo-fascism.’”

Today, however, that “sense of purpose” seems to have found its object in Russia. The crusade against Putin has taken the place of the crusade against Saddam. Jonathan Chait is a representative case. Once a prominent liberal cheerleader for the wars in Iraq and Libya, he now takes to the pages of New York magazine to spin conspiracy theories regarding Trump and Russia.

But by linking arms with the neocons in their opposition to Trump, liberal Democrats are effectively laundering the reputations of unapologetic war enthusiasts such as Kristol and Frum, and assisting them in whitewashing their records. Painfully learned and expensive lessons from the United States’ ill-starred military adventures over the last decade and a half are now all but ignored by too many US political and media elites.

Still worse, the neocon-Democratic alliance crowds out space for the few remaining progressive, ethical realists in a party still dominated by the liberal hawks.

With the midterms in sight and another presidential election cycle soon to follow, now seems the time for Democrats to make clear (finally) that there is no place in the party for neocon war hawks; that the liberal flirtation with (if not outright admiration for) folks like Frum, Boot, and Kristol has gone too far; and to recognize that neocon influence will undercut efforts within the party by members (and future members) of Congress like Ro Khanna, Mark Pocan, Barbara Lee, and Alexandria Ocasio-Cortez, to fashion a sensible alternative to the unrestrained militarism that passes for American foreign policy today.

In terms of policy, the alliance between liberal Democrats and neocons is already having an effect: They have made common cause with regard to the desirability of regime change in Syria and the undesirability of either peace with North Korea or détente between Russia and the West. And in so doing, they have helped to define these as the “mainstream” positions, opposition to which results in swift marginalization, and, more often than not, personal vilification.

By shunning a sensible, prudent, ethical foreign policy—one with roots stretching as far back as George Washington and John Q. Adams—in favor of what is essentially a policy of militarism run amok, liberals are demonstrating, in a phrase articulated long ago by Walter Lippmann and Charles Merz, a “boundless credulity, and an untiring readiness to be gulled.”

Democrats be warned: Embracing the neocons is not the way to oppose Mr. Trump. Doing so may instead pave the way for his reelection.