The white nationalist Richard Spencer was on vacation in Japan when he learned that Hillary Clinton was planning to give a speech about Donald Trump’s ties to the so-called alt right, and he was thrilled. “It’s hugely significant,” Spencer told me by Skype from Kyoto. “When a presidential candidate—and indeed the presidential candidate who is leading in most polls—talks about your movement directly, I think you can safely say that you’ve made it.”

Spencer, a clean-cut 38-year-old, loves publicity. He hung around last month’s Republican National Convention in Cleveland with a sign saying, “Wanna Talk to a ‘Racist’?” He is president and director of the National Policy Institute, described on its website as “dedicated to the heritage, identity, and future of people of European descent in the United States, and around the world.” He coined the term alternative right, founding the website alternativeright.com in 2010, which has since morphed into the highbrow racist RadixJournal.com. “The alt right has really become the banner for European identity politics in the United States and around the world,” he said. Spencer agrees with Clinton about very little, but he agrees with her about this: Understanding the alt right is important to understanding Trump’s rise.

Clinton’s speech about the alt right is scheduled for Thursday in Reno, Nevada. “Trump’s newly installed brain trust of Steve Bannon, Roger Ailes and Roger Stone completes Donald Trump’s disturbing takeover of the Republican Party,” said a statement by Clinton campaign chairman John Podesta, citing Trump’s new campaign CEO as well as his informal advisers. “We intend to call out this ‘alt-right’ shift and the divisive and dystopian vision of America they put forth because it tells voters everything they need to know about Donald Trump himself.”

For the alt right, a movement nurtured on internet message boards and websites full of obscure in-group jargon, such a high-profile denunciation is a big deal. The white nationalist website VDARE is already fundraising off the speech. Yet it is Trump, not Clinton, who has given the alt right unprecedented political relevance. It’s not just that he’s a hero to the movement. He has actively helped expand its reach. He retweets white supremacist accounts and echoes alt-right rhetoric about America’s devolution into a violent mongrel hellscape, besieged by immigrants from without and crime and disorder from within. Trump shares the alt right’s respect for Vladimir Putin, admired by many in the alt right as the leader of what Spencer calls “a powerful white empire.” (By contrast, said Spencer, the countries of NATO are “cucked nations”—cuck being a favorite alt-right insult, invoking white men who are cuckolded by black men.) Trump’s comparisons of Clinton to Angela Merkel might have puzzled many Americans—Germany’s chancellor isn’t a household name here—but as ThinkProgress reported, white supremacists who revile Merkel for her policy on migrants have been making the same connection for months.

Until recently, the overlap between Trump and the alt right seemed more a matter of what Spencer calls “elective affinities” than active coordination. But earlier this month, Trump hired Bannon, then chairman of Breitbart News, to be his campaign’s CEO. Bannon has run Breitbart since the death in 2012 of its eponymous founder, Andrew Breitbart, turning the site in an explicitly ethno-nationalist direction. “We’re the platform for the alt-right,” Bannon told the journalist Sarah Posner last month.

Now the Clinton campaign has to try and explain to America what the alt right is. That might not be easy. Though Spencer came up with the term, it has come to define a broader congeries of reaction. The alt right encompasses longstanding racist organizations; taboo-scorning Twitter trolls; unapologetic misogynists; professional Islamophobes; and so-called neo-reactionaries, a movement of futuristic monarchists. What unites these figures is a fundamental rejection of egalitarianism, contempt for democracy, and irreverent glee in their ability to shock the bourgeoisie. Daryle Lamont Jenkins, who founded the One People’s Project to track the far right, describes the alt right as “hipster Nazis.”

The alt right generally sees itself as being at war with establishment conservatism. “The Alt Right is one name for the political tendency (actually tendencies) that exist outside of the racket of Conservatism Inc.—the GOP publicists, cheerleaders and assorted parasites who make up the Establishment Right,” Peter Brimelow, the editor of VDARE, told me via email. “It addresses new issues that have surfaced since the end of the Cold War, like immigration, Affirmative Action, the emerging science of race differences, even rethinking foreign policy etc., all of which are currently kept out of public debate by the curse of Political Correctness.”

Ironically, for a movement obsessed with nationalism, the alt right has more affinity with the European right than traditional American conservatives do. United by ethnicity rather than religion, it is less moralistic than the Christian right; like the right in Europe, it is more likely to condemn Muslim homophobia than to condemn homosexuals. The big alt-right event at the Republican National Convention was the Gays for Trump party hosted by Milo Yiannopoulos, Breitbart’s technology editor, which drew Spencer, Brimelow and Dutch right-wing politician Geert Wilders. The alt right sees allies in France’s National Front and Britain’s U.K. Independence Party, whose leader, Nigel Farage, rallied with Trump on Wednesday night in Mississippi.

For alt-right apologists, the movement’s decadent impudence serves as an alibi; they say its bigotry shouldn’t be taken at face value. In March, Breitbart published “An Establishment Conservative’s Guide to the Alt-Right,” by Yiannopoulos and Allum Bokhari. “Just as the kids of the 60s shocked their parents with promiscuity, long hair and rock’n’roll, so too do the alt-right’s young meme brigades shock older generations with outrageous caricatures, from the Jewish ‘Shlomo Shekelburg’ to ‘Remove Kebab,’ an internet in-joke about the Bosnian genocide,” they wrote. “Are they actually bigots? No more than death metal devotees in the 80s were actually Satanists.” When Britain voted to leave the European Union, Yiannopoulos tweeted, “Sorry about it (((Soros))),” accompanied by a photo of a little blond girl. He was referring to the liberal financier George Soros, and the triple parentheses are the alt-right symbol for Jew. This was apparently arch, ironic anti-Semitism, not the vulgar earnest kind. (Yiannopoulos has been permanently banned from Twitter, so the tweet is no longer available.)

Spencer, however, is dead serious about his ideas, despite his taste for sarcasm and memes. “European identity politics is really an inevitability,” he said. “It’s going to happen in North America as whites become a minority in this country. And the only question really is how it is going to happen. I never would have predicted that it would happen through Donald Trump. If you had told me that two years ago, I would have said you were crazy. But it is happening.”

He’s right, it is. Now Clinton has to make it clear to America what that means.

Read more Slate coverage of the 2016 campaign.