WASHINGTON — For many Trump supporters, the inauguration of Joseph R. Biden Jr. this week will be a signal that it is time to move on. The president had four years, but Mr. Biden won, and that is that.

But for a certain slice of the 74 million Americans who voted for President Trump, the events of the past two weeks — the five deaths, including of a Capitol Police officer, the arrests that have followed, and the removal of Mr. Trump and right-wing extremists from tech platforms — have not had a chastening effect.

On the contrary, interviews in recent days show that their anger and paranoia have only deepened, suggesting that even after Mr. Trump leaves the White House, an embrace of conspiracy theories and rage about the 2020 election will live on, not just among extremist groups but among many Americans.

“I can’t just sit back and say, ‘OK, I’ll just go back to watching football,’” said Daniel Scheerer, 43, a fuel truck driver in Grand Junction, Colo., who went to the rally in Washington last week, but said he did not go inside the Capitol and had nothing to do with those who did. He said he did not condone those who were violent, but believed that the news media has “totally skewed” the event, obscuring what he sees as the real story of the day — the people’s protest against election fraud.

“If we tolerate a fraudulent election, I believe we cease to have a republic,” he said. “We turn into a totalitarian state.”

Asked what would happen after Mr. Biden took office, Mr. Scheerer said: “That’s where every person has to soul search.”

He continued: “This just isn’t like a candidate that I didn’t want, but he won fair and square. There’s something different happening here. I believe it needs to be resisted and fought against.”

Mr. Scheerer said he was not advocating violence, nor was he part of any group that was. But he echoed the views of many who supported the events in Washington last week: A fervent belief that something bad was about to happen, and an instinct to fight against it.

Polls indicate that only a small fraction of Americans approved of the riot in Washington last week. A Washington Post-ABC News poll showed that 8 percent of adults and 15 percent of Republicans support “the actions of people who stormed the U.S. Capitol last week to protest Biden’s election as president.” That is far from most voters, but enough to show that the belief in a stolen election has entered the American bloodstream and will not be easy to stop.

“It’s a dangerous situation,” said Lucan Way, a political scientist at the University of Toronto who writes about authoritarian regimes. “The ‘election was stolen’ narrative has become part of the political landscape.”

The country’s political divide is no longer a disagreement over issues like guns and abortion but a fundamental difference in how people see reality. That, in turn, is driving more extremist beliefs. This shift has been years in the making, but it went into hyper-speed after the Nov. 3 election as Mr. Trump and many in his party encouraged Americans, despite all the evidence to the contrary, to believe the results were fraudulent. The belief is still common among Republicans: A Quinnipiac poll published Monday found that 73 percent still falsely believe there was widespread voter fraud.

Now, with Mr. Biden’s inauguration on Wednesday and so many Americans enraged about the election, state capitals and Washington are on high alert, with soldiers and security perimeters, bracing for further acts of violence.

“Polarization is not the problem anymore,” said Lilliana Mason, a political psychologist at the University of Maryland. “Now it’s the threat to democracy.”

When Professor Mason began surveying people in 2017 about their tolerance for political violence for a book on partisanship, she did not expect to find much. Partisanship was always seen as an inert, harmless thing, she said, a way to get people interested in the otherwise boring topic of politics.

She was wrong. She and her co-author, Nathan Kalmoe, found that the share of Americans who say it is “at least a little bit justified” to engage in violence for political reasons has doubled in three years, rising to 20 percent after the election, from 10 percent in 2017. The trend was the same for both Republicans and Democrats. But the election was a catalyzing event: The Republicans who said they condoned violence became more approving after it, Professor Mason said. Democrats stayed about the same.

Professor Mason said she worried that more violence and attacks on elected leaders and state Capitols could be coming, saying the country could be in for a period like the Troubles, the conflict in Northern Ireland in which sectarian violence kept the region unstable for 30 years.

In interviews with Mr. Trump’s more fervent supporters, people expressed a pattern of falsehoods and fears about the coming Biden administration. As events like the riot have raced ahead, so have conspiracy theories explaining them. They have blossomed in the exhausting monotony of coronavirus lockdowns.

Theda Kasner, 83, a retired medical worker from Marshfield, Wis., who was originally interviewed for a New York Times polling story before the election, has been in an R.V. park in Weslaco, Texas, near the border with Mexico, since December. She is spending the winter there with her husband, for the sun and the beaches nearby. But the coronavirus is roaring through, and this week, their R.V. park went on lockdown.

“I told my husband today, I said ‘I’m going stir crazy,’” she said. “We are practically quarantined in our units.”

She has been spending lots of time in her motor home reading books and watching videos. One featured rousing, emotional music and footage of Mr. Trump and crowds of his supporters, with a voice talking darkly about a looming confrontation. It ended with the Lord’s Prayer and the date Jan. 20, 2021, flashing on the screen. Another, 48 minutes long, was of Jovan Hutton Pulitzer, an inventor, testifying before the Georgia State Senate about election fraud. She and her husband watch Newsmax TV, a right-wing network, in the evenings.

When asked about the violence at the riot, Ms. Kasner repeated the common conspiracy theory that antifa had infiltrated the crowd. These days, she is finding herself increasingly confused in a sea of information, much of it false.

She had heard on a video she was sent on Facebook that in the Biden administration, children could be taken away from their parents. “I am in a total state of, I don’t know what is happening,” Ms. Kasner said.

“I simply cannot fathom what my country is becoming,” she said, saying that she had been sitting in her home in tears.

For Mr. Scheerer, the fuel truck driver in Colorado, the multiple catastrophes of the past year — the coronavirus, the economic disruption that came with it, the political fear across the country — all fused into a kind of looming threat. The lockdowns infuriated him. He sees mask mandates not as public health but public control. Both, he believed, were signs of a coming tyranny. He left a truck-driving job he liked when, by his account, his boss told him he had to wear a mask or leave.

Then came the election.

On Jan. 6, he arrived in Washington for the rally to protest the results. Afterward, when pressed on how he felt about the event given the number of white supremacists in the riot, he said that they were only a fraction of the people there. Anyway, he said, their presence was insignificant compared the broader issue of fraud.

“It’s way more than just being some kind of a Trump fanatic,” he said. He said he sees himself as “a guy up on the wall of a city seeing the enemy coming, and ringing the alarm bell.”

Force he said, is only a last resort.

“Are you OK with internment camps if you refuse to wear a mask or take a vaccination?” he asked. “I believe in a world where force has to be used to stop evil or the wrong act.”

In western North Carolina, Kevin Haag, a retired landscaper who was at the Capitol last week but did not go inside, said people in his conservative community have grown increasingly alarmed about what has happened in the days since. His electric power company, Duke Energy, has announced it would pause donations for Republicans who voted against certifying the election results. It all feels like a vast piling on against Trump supporters, he said.

To top it off, the Senate, the House and the White House now belong to Democrats.

“Now it’s pretty scary, people are alarmed, they own it all now,” said Mr. Haag, who was first quoted in a Times story about the December rally in Washington for Mr. Trump. Mr. Haag, who is 67, is also a member of his local town council.

In a telephone conversation this week, he said he is part of a group called the Armed Patriots, people from his area whose purpose, he said, is to protect the community. On Tuesday night, the group met, he said, and invited the public for a gun instruction session with two experts who talked about how to use an assault rifle. Sixty people attended, he said, including women.

They also held a raffle of a gun to raise money for a website, he said, “because they are taking down our communications.”

The meeting, he said, “was to educate and to relieve fear.”

Mr. Haag insisted that the group was not a militia.

“We are not here to take over the country,” he said. “If that’s what you are here for, we are not your group. We are here to protect our citizens and to stand up for our country.”

He said he was still hoping that Mr. Trump would be the one to be inaugurated this week. But even if Mr. Trump did not succeed, the movement, he said, would continue.

“It’s not about Trump, he was just championing the cause,” he said. “We don’t have Trump around right now, and we are picking up the ball and running with it ourselves.”

Kitty Bennett contributed research.