Some years ago, while on a camping trip with my family in Joshua Tree National Park, I stopped by a local grocery store to get some firewood. At the checkout counter, I found myself behind a white man buying diapers and baby formula. As he reached for a pack of gum from the display rack, his shirt sleeve lifted, revealing a tattoo of SS lightning bolts. I recoiled in horror, but he seemed entirely unconcerned. To him, I was just another tourist in hiking clothes. To me, though, his presence was indelible—the white supremacist in the checkout line.

I thought of him again last month, when federal officials announced the arrest of Christopher P. Hasson, a Coast Guard lieutenant who planned to “murder innocent civilians on a scale rarely seen in this country.” A self-proclaimed white nationalist, Hasson had reportedly admired the Norwegian terrorist Anders Breivik, pondered the use of biological weapons and attacks on food supplies, and created a spreadsheet of targets that included prominent reporters and Democratic politicians. Hasson had previously spent five years in the Marines and two in the Army National Guard, slowly rising through the ranks without attracting notice for his dreams of a “white homeland.”

The Hasson case is but one example of white extremism in the United States. Two years ago, hundreds of white nationalists—including six active-duty and former members of the military—marched through Charlottesville, Virginia, chanting: “Jews will not replace us!” Last year in Kentucky, Gregory A. Bush tried to enter a black church but, after failing at this goal, shot and killed two black customers in a Kroger supermarket, while sparing the white one. (“Whites don’t kill whites,” Bush told him.) Also last year, Robert D. Bowers, angered by the involvement of the Pittsburgh Tree of Life synagogue in refugee resettlement, killed 11 people there during a bris ceremony. It was the largest anti-Semitic attack in the country’s history.

The trend is extremely worrisome. According to the Anti-Defamation League, the overwhelming majority of fatal attacks by extremists in the United States last year were perpetrated by right-wing domestic extremists. Yet white nationalists continue to evade detection, and it’s not exactly difficult to figure out why. Between 2002 and 2017, the Department of Homeland Security spent an astounding $2.8 trillion on counter-terrorism efforts, most of it to fight Islamist groups like Al Qaeda and ISIS, both at home and abroad. Domestically, the Countering Violent Extremism Task Force has focused on immigrant organizations and Black Lives Matter activists.

By comparison, elected officials seem uninterested in the threat posed by white extremists. The House of Representatives held multiple hearings on the 2012 attack on the US consulate in Benghazi, once grilling Hillary Clinton for 11 hours, but it has not tackled the white-nationalist attacks in this country. Likewise, the Senate Armed Services Committee routinely hears from experts about foreign threats, but it has not requested an official investigation into the white nationalists in the military.

At a news conference held after Hasson’s arrest, a reporter asked Donald Trump if he thought he should moderate his rhetoric. “No, I don’t,” the president replied. “I think my language is very nice.” Trump, of course, has referred to the neo-Nazis who marched through Charlottesville as “fine people” and has called the news media “the enemy of the American people.” He has run an anti-Semitic campaign ad, retweeted white-nationalist accounts on Twitter, and won the praise of former Ku Klux Klan Grand Wizard David Duke.

Yet it is Democratic Congresswoman Ilhan Omar who has made news concerning the rise of anti-Semitism in this country. In a tweet she says was intended to criticize AIPAC’s lobbying on behalf of Israel, Omar invoked “the Benjamins” and, a few days later, blasted those who would “push for allegiance to a foreign country,” leading members of both parties to accuse her of spreading hateful tropes. “It is shameful that House Democrats won’t take a stronger stand against [a]nti-Semitism in their conference,” Trump tweeted. He was joined by a growing chorus of Republicans, who insisted on Omar’s censure and even resignation from her committee seats. In the end, House Democrats passed a resolution condemning hate in all its forms—with 23 Republicans opposed.

As the controversy took over the headlines, I wondered again about the white supremacist in the checkout line. Was he paying attention to the language in the House resolution? He might be a man of action rather than words. Perhaps, like Christopher Hasson, he used his work computer to study the manifestos of mass shooters. Or perhaps he had no immediate plans but took the long view, working to elect people who would represent his positions. Earlier this month, leaked chat logs from members of the white-supremacist group Identity Evropa revealed that they had donated to Congressman Steve King’s campaign and called members of Congress to express support for him. (King is the nine-term congressman from Iowa who recently wondered when phrases like “white nationalist” and “white supremacist” had become offensive.)

White supremacy has always been part of this nation’s history. The US Constitution, written by wealthy white landowners, was designed to keep power in the hands of white men. Although that power has continually been contested, it has never been relinquished without a struggle. Only in the last few decades have Americans of different national, religious, and ethnic backgrounds begun to enjoy the full rights and privileges of citizenship.

In fact, America is becoming increasingly diverse: A child born today is as likely to be white as nonwhite. Despite this, or perhaps because of it, white nationalism is back with a vengeance. Defeating it will be the moral, electoral, and educational challenge of a generation.