When Donald Trump hired Breitbart's Steve Bannon to lead his campaign, the alt-right rejoiced. Not only had one of their own made it into the halls of power, he was seated at the right hand of the candidate who has done more to advance their politics of white nationalism, men's rights and conspiracism than any nominee in a generation or more.

As the Trump campaign embraces its alt-right identity, mainstream conservatives are confronted with a challenging future. A break with the alt-right might slim the right's ranks, but merging with it endangers the future of conservatism altogether.

Breitbart, the right-wing news organization Bannon runs, is key to the story of the alt-right's power in this election. Tell an adherent of the alt-right that Breitbart is an alt-right site and they'll scoff. (If you're a guy, they'll call you a "cuck," a reference to emasculated white manhood. If you are a woman, they'll use a different four-letter c-word.) Breitbart isn't the beating heart of the alt-right but the entering wedge, the link between the alt-right and the mainstream right.

Earlier this year, Breitbart published a piece by Allum Bokhari and Milo Yiannopoulos that served as an alt-right manifesto. Read it if you like, but it basically boils down to "we're smarter than rednecks and less hate-filled (but not necessarily less racist) than neo-Nazis." The alt-right is devoted to white nationalism, making it comfortably at home on white supremacists sites like VDARE, but also to aggrieved masculinity in the form of men's rights activism.

Little wonder they see a kindred spirit in Trump, who likes to talk about his excellent genes and sizable penis. But the deeper reason they love Trump so much is that he repeatedly condemns political correctness. Political correctness is the alt-right's most cherished concept, because it is cover for their most odious ideas. Racism, misogyny, anti-Semitism – all are simply "telling it like it is" in the face of the PC police. When Trump denounces political correctness, then pledges to deport Mexicans and ban Muslims, he fortifies the alt-right's worldview.

Bringing Bannon on board, then, does more than bring conservative media into Trump's campaign. It brings in the alt-right. And with Sean Hannity and Roger Ailes coming aboard as unofficial advisers, the threat of a conservative schism looms large. You can see it brewing in conservative media. Breitbart delights in skewering Glenn Beck, the one-time tea-party mainstay. National Review, which has published some damning pieces on the alt-right, leads the #NeverTrump resistance. Meanwhile rumors have been circulating of a post-election Trump network to challenge Fox News (something the Washington Post's Greg Sargent wrote about earlier this week).

The greater threat, though, is not that the alt-right breaks off from mainstream conservatism but that it merges with it. In some ways, it already has. Trump is the Republican nominee, after all, and still has the support of most of the Republican Party. And last week National Review writers were debating the pluses and minuses of white identity politics, no doubt a welcome sign to those alt-rightists looking for friendly faces within mainstream conservatism.

But unity is not worth the price. Welcoming the alt-right would permanently damage the conservative project. It would elevate populism over policy, racism over reform and nihilism over institution-building. The alt-right would poison the entire movement with its reactionary politics.

Many conservative recognize this. There has been talk of a post-election purge, similar to what National Review did to the Birch Society after Barry Goldwater's loss in 1964. Tired of being tarred as wild-eyed extremists because of their connection to the conspiracy-minded Birch Society, National Review editors drew a line between responsible conservatives and irresponsible conservatives, effectively disowning the Birchers.

Yet those looking for a replay of that 1964 purge will be sorely disappointed. The #NeverTrump forces don't command the same authority National Review did in the much-smaller conservative movement of the 1960s. What's more, it's not clear there can be any gatekeeping in the anti-establishment era of American conservatism. The conservatives of the 1960s weren't looking to smash all institutions, to end all orthodoxies. They thought authority was a good thing, but believed it had fallen into the wrong hands.