If the United States’ failure to anticipate the terrorist attacks of Sept. 11, 2001, was one of imagination, missing the terrorist attack of Jan. 6, 2021, was a failure of perception — a persistent refusal at the highest levels of our government to acknowledge the empirical reality of the threat posed by right-wing terrorists.

Terrorism in the United States is overwhelmingly domestic and motivated by far-right ideologies, often racist, anti-Semitic, anti-Muslim and anti-immigrant. In the past decade — indeed, in just about every year since 1990, other than 2001 — acts of right-wing domestic terrorism have been far more numerous and more lethal than acts of terrorism inspired or influenced by groups or movements overseas, according to the National Consortium for the Study of Terrorism and Responses to Terrorism, a research center at the University of Maryland. Far-right plots are also less likely to be disrupted by law enforcement; in the past decade about two-thirds of right-wing domestic terrorist plans have ended in “success,” according to the center, compared with 22 percent of terrorist plans hatched by international and affiliated actors.

So one of the most striking passages in President Biden’s Inaugural Address on Wednesday was also one of the most straightforward: He named the enemy. “Political extremism, white supremacy” and “domestic terrorism,” he said, are dangers “that we must confront and we will defeat.”

It was a quick line delivered without much flourish, and it may sound overgenerous to congratulate Biden simply for speaking plainly. Yet it is a sign of how reluctant American officials have been to take on right-wing violence that his line made history. He may be the first president to directly address white supremacy — a stain on the United States since before its founding — in an Inaugural Address.

Incantation alone cannot solve any problem, of course. But in the fight against far-right attacks, a president’s naming the menace might at least push the nation out of the ditch of inaction we’ve been stuck in for decades.

The primary reason that right-wing political violence persists in the United States is that it has rarely been prioritized by law enforcement, and the primary reason it has rarely been prioritized is political reluctance to do so. In the past decade, the lethal attacks kept coming — at a Black church in Charleston, S.C.; at a synagogue in Pittsburgh; at a Walmart in El Paso; at a protest against a racist rally in Charlottesville, Va., — but under Donald Trump and even under Barack Obama, security officials continued to shower resources on addressing foreign threats rather than those closer to home.

The government’s lapse has now become obvious. In the months leading up to the Capitol riot, right-wing assailants hardly attempted to hide their intentions. Many promised in public that they were planning to attack the government. They photographed themselves preparing to attack the government. They posted the routes they planned to take on their way to attack the government. Some even practiced attacking the federal government by attacking state governments. Undoing their plot was not a matter of finding a needle in a haystack; this was more like searching for a porcupine in a haystack, unmissable by anyone who cared to take minimal notice.

And yet the counterterrorism community still missed this huge attack — just as experts had long predicted would happen.

“Many of us in the counterterrorism community were feeling frustrated that we couldn’t quite drive progress the way we thought it needed to be driven,” said Elizabeth Neumann, who was an assistant secretary of counterterrorism and threat prevention in Trump’s Department of Homeland Security.

Much of this problem was instigated and exacerbated by Trump himself. With the president winking at and even encouraging right-wing violence while falsely claiming that left-wing groups were the real problem, it’s hardly surprising that federal law enforcement would downplay the issue. Last year a whistle-blower charged that Homeland Security officials delayed publishing an assessment that declared white supremacy the “most persistent and lethal threat in the homeland” in order to align the agency’s message with Trump’s; the department finally published the document late last year.

Republican politicians and luminaries of conservative media have also cultivated cozy ties with the far right. Gavin McInnes, a founder of the Proud Boys, an extremist group whose members took part in the Capitol riot, has appeared dozens of times on Fox News. A leader of Stop the Steal, one of the groups that organized the Capitol protest, has claimed that it coordinated with some Republican members of Congress — who now may face legal trouble. There is also right-wing gun culture, which has become intertwined with white supremacy. A 2017 ad by the National Rifle Association divides the country into “ours” and “theirs,” leaving little question about the skin color of “ours.”

But doubt about the threat posed by domestic terrorists extended beyond Trump and other conservatives. Neumann told me that there was a sense among many in law enforcement that Americans could not cause great harm — domestic terrorists were “lone wolves,” they were disorganized and uncoordinated, their danger was nothing existential. There was some truth to this belief, Neumann acknowledged, but the view was so fixed that it created its own warped reality.

In the absence of leaders declaring that “this is the threat that we’re facing and we’re going to leverage all our tools in our tool kit to go after it,” Neumann said, misinformation and disinformation clouded the issue, which is why many so many Americans are unaware of the prevalence of far-right terrorist acts — which, in turn, is why there’s little political focus on it.

After acknowledging the problem, there are several practical steps the Biden administration might take to address right-wing violence. Many of these are obvious, following the lessons that counterterrorism officials have learned investigating Islamic terrorism.

Experts I talked to called for vigilant investigation and prosecution of the Capitol rioters; more resources for anti-radicalization programs, which have proved effective in countering jihadi recruitment; a much greater federal emphasis on investigating hate crimes, acts of ideologically motivated violence that often fly under the radar of terrorism investigators; continued deplatforming of right-wing agitators from mainstream media; and greater cooperation between the United States and other countries in tracking and preventing attacks and recruitment that crosses borders, a growing problem in a digital world.

But the most important political move Biden can make is simply to keep shining a bright light on this scourge. Trump often mocked Democrats for refusing to say the phrase “radical Islamic terror,” as if that were a spell that could make ISIS vanish. It wasn’t — but asking Republicans to repeatedly and specifically disavow radical white terrorism wouldn’t be a bad place to start.

Office Hours With Farhad Manjoo

Farhad wants to chat with readers on the phone. If you’re interested in talking to a New York Times columnist about anything that’s on your mind, please fill out this form. Farhad will select a few readers to call.

The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: letters@nytimes.com.

Follow The New York Times Opinion section on Facebook, Twitter (@NYTopinion) and Instagram.