WHITEFISH, Mont. — Richard B. Spencer, the most infamous summer resident in this town, once boasted that he stood at the vanguard of a white nationalist movement emboldened by President Donald J. Trump. Things have changed.

“I have bumped into him, and he runs — that’s actually a really good feeling,” said Tanya Gersh, a real estate agent targeted in an antisemitic hate campaign that Andrew Anglin, the founder of the Daily Stormer, a neo-Nazi website, unleashed in 2016 after Mr. Spencer’s mother made online accusations against Ms. Gersh.

Leaders in Whitefish say Mr. Spencer, who once ran his National Policy Institute from his mother’s $3 million summer house here, is now an outcast in this resort town in the Rocky Mountains, unable to get a table at many of its restaurants. His organization has dissolved. Meanwhile, his wife has divorced him, and he is facing trial next month in Charlottesville, Va., over his role in the deadly 2017 neo-Nazi march there, but says he cannot afford a lawyer.

The turn of events is no accident. Whitefish, a mostly liberal, affluent community nestled in a county that voted for Mr. Trump in 2016 and 2020, rose up and struck back. Residents who joined with state officials, human rights groups and synagogues say their bipartisan counteroffensive could hold lessons for others in an era of disinformation and intimidation, and in the wake of the Jan. 6 Capitol riot.

“The best way to respond to hate and cyberterrorism in your community is through solidarity,” said Rabbi Francine Green Roston of the Glacier Jewish Community/B’nai Shalom, who now lectures other groups on how to ward off hate campaigns like the one Whitefish endured. “Another big principle is to take threats seriously, and prepare for the worst.”

Mayor John Muhlfeld agreed. “You have to act swiftly and decisively and come together as a community to tackle hate and make sure it doesn’t infiltrate your town,” he said.

On Saturday, Mr. Spencer said he kept a “very low profile” in Whitefish, and though he had been denied service in local establishments in the past, “I don’t have any anxiety dealing with anyone.” He said he does not run from Ms. Gersh and understood why people would be angry with him.

“I don’t want any battles with them here in Whitefish,” he continued, “and I hope they take a similar attitude, that it’s best to move on.” His mother, Sherry Spencer, did not respond to requests for comment.

Advice and an Accusation

The trouble in Whitefish started after Mr. Trump’s victory in the 2016 election that November. Mr. Spencer, who had called his white nationalist movement a “vanguard” for Mr. Trump, delivered a racially charged speech at his institute’s conference in Washington, his words greeted by Nazi salutes. Video of the address went viral. In Whitefish, residents discussed protesting in front of a downtown commercial building owned by Mr. Spencer’s mother.

Ms. Gersh said Ms. Spencer had called her.

“She flat-out asked me, ‘Tanya, I don’t believe in my son’s ideology,’” Ms. Gersh recalled over coffee in her office downtown. “‘I’m heartbroken that this is hurting Whitefish. What should I do?’”

“I said: ‘Sherry, if this were my son, I would go ahead and sell the building. I would donate some money to something like the Human Rights Network to make a statement, and publish that you don’t believe in the ideologies of your son.’ And she said: ‘Thank you, Tanya. That’s exactly what I should do.’”

Ms. Gersh said she had arranged to sell the property without making any profit. But a short time later, she said, Ms. Spencer sent an email saying she had changed her mind about working with Ms. Gersh. Ms. Gersh supplied names of other real estate agents.

Two weeks later, in December 2016, Ms. Spencer posted an article on the open publishing platform Medium accusing Ms. Gersh of using the threat of protests to blackmail her into selling. Mr. Spencer said on Saturday that he and his former wife had written the article published under his mother’s name. He repeated their claims against Ms. Gersh, adding that she had called his mother, not the other way around. The Spencers’ accusations quickly reverberated among the far right. Mr. Anglin of the Daily Stormer exhorted his “fam” online to “TAKE ACTION” to defend Ms. Spencer.

He shared personal information and the social media accounts of Ms. Gersh and her family, including her son, then 12. A post in which Mr. Anglin encouraged his followers to “stop by and tell her in person what you think of her actions” was the first of some 30 articles he published targeting the Gersh family and the Jewish community in Whitefish, according to a lawsuit Ms. Gersh filed in 2017 against Mr. Anglin in U.S. District Court in Montana.

Ms. Gersh received hundreds of text messages, emails and Christmas cards threatening her. Her voice mail filled up several times a day. Hateful comments about Ms. Gersh appeared on real estate websites. Homeowners were afraid to list with her.

The campaign swept in Rabbi Roston, another area rabbi and his wife, and any Whitefish residents and business owners the trolls believed were Jewish.

At one point, Rabbi Roston realized one of the anonymous antagonists was the father of her son’s best friend. Her family did not confront the man, who has since moved away. “He had a lot of guns,” she said.

Mr. Anglin next announced a march on Whitefish, planned for Martin Luther King’s Birthday in 2017. An ad for the event depicted the gates of the Auschwitz death camp with photos of Ms. Gersh, her son, Rabbi Roston and the other rabbi’s wife superimposed.

The march was planned to end at the Gersh home.

‘A Full Plan in Place’

Whitefish and Montana mobilized.

Montana’s governor, attorney general and congressional delegation issued a bipartisan open letter, making it clear “that ignorance, hatred and threats of violence are unacceptable and have no place in the town of Whitefish, or in any other community in Montana or across this nation.” The governor at the time, Steve Bullock, wrote editorials condemning the antisemitic campaign and met with the families in Rabbi Roston’s home.

As tensions rose in Whitefish, Mr. Spencer and his parents made public statements distancing themselves from the march and from Mr. Anglin. Behind the scenes, the police and the federal authorities readied themselves for a potentially violent event.

Mr. Muhlfeld, the mayor, said that the town had not refused Mr. Anglin a special event permit but that Mr. Anglin had not met the town’s conditions, including a prohibition on firearms.

“If you asked, ‘Do you think they’re going to show up?’ they were like, ‘Nah,’ but they had a full plan in place,” Rabbi Roston said. “If you look at Jan. 6, the quickness with which people wrote off threats was dangerous,” she added.

The Anti-Defamation League, the Southern Poverty Law Center and the Secure Community Network, the official safety and security organization of the North American Jewish community, advised residents on what to do.

As a result, Ms. Gersh did not speak publicly about her ordeal at the time. Rabbi Roston kept a low profile, discouraging coverage in the Jewish news media to protect the congregation and avoid giving attackers the attention they craved. The congregation did not cancel its Hanukkah party in December 2016 but moved it from the rabbi’s home to the conference room of a motel, with two armed security guards at the door. On each table, the rabbi placed a pile of supportive letters that had arrived from around the nation.

Volunteers distributed thousands of paper menorahs. “There were menorahs in every window in Whitefish,” Ms. Gersh said. An anti-hate rally drew 600 participants in zero-degree weather. On the eve of the neo-Nazi march, Rabbi Roston organized a chicken and matzo ball soup get-together for 350 people at the middle school in Whitefish, in a demonstration of unity and appreciation.

On Martin Luther King’s Birthday — Monday, Jan. 16 — not a single neo-Nazi turned up to march. “We could say they chickened out,” Rabbi Roston joked.

In April, Ms. Gersh, represented by the Southern Poverty Law Center, filed suit against Mr. Anglin for invasion of privacy, intentional infliction of emotional distress and violations of Montana’s Anti-Intimidation Act. In 2019, she won $14 million in damages. A team of lawyers is still searching for Mr. Anglin and his assets.

The trial in the Charlottesville case, Sines v. Kessler, begins on Oct. 25. A group of victims and counterprotesters filed suit against Mr. Anglin as well as Mr. Spencer, along with nearly two dozen people and groups involved in the “Unite the Right” rally, after a neo-Nazi at the Charlottesville march plowed his car into a crowd of counterprotesters, killing Heather Heyer, 32, and injuring at least 19 others.

Mr. Spencer’s lawyer withdrew from the case last year because he had not been paid. “Due to deplatforming efforts against me, it is very difficult for me to raise money as other citizens are able to,” Mr. Spencer told the judge in a pretrial hearing in 2020. He is now representing himself.

As the trial approaches, the case has generated a number of contempt-related fines and sanctions against the defendants.

“After four years of so little accountability, it’s important to make clear that accountability matters and it works,” said Amy Spitalnick, the executive director of Integrity First for America, the nonprofit group that brought the lawsuit.

Separately, in May, a federal judge in Ohio ordered Mr. Spencer’s National Policy Institute to pay $2.4 million to William Burke, a counterprotester who was severely injured in Charlottesville.

Mr. Muhlfeld said he had last seen Mr. Spencer in 2019, skiing at the mountain resort. “He walked into the Summit House and summarily was booed by pretty much everyone,” Mr. Muhlfeld said, referring to a restaurant there.

“Richard Spencer wanted this to be his happy vacation place where he could play and have fun, and people would just live and let live,” Rabbi Roston said. “Then he started suffering social consequences for his hatred.”

Ms. Gersh said that she had been afraid to work again after the hate campaign, but that after Charlottesville, “I knew that I had to go back to work because if I didn’t, they win.”

She keeps a photo of Ms. Heyer on her desk and bear spray in its drawer.

Kitty Bennett contributed research.