An Oath Keeper Was at the Capitol Riot. On Tuesday, He’s on the Ballot.

Edward Durfee Jr. is many things: a former Marine, a libertarian who distrusts the Federal Reserve and an active member of the far-right Oath Keepers militia who leads the group’s northern New Jersey region and was outside the Capitol during the Jan. 6 attack.

He is also running for the New Jersey State Assembly as a Republican.

More than 20 Oath Keepers have been charged in connection with the Jan. 6 attack. Prosecutors have accused members of the militia of plotting to overturn the election by breaching the Capitol and making plans to ferry “heavy weapons” in a boat across the Potomac River into Washington.

Mr. Durfee, a 67-year-old tech consultant, said he did not enter the Capitol during the assault, and he condemned the violence that led to several deaths.

But he wholeheartedly embraces the ideology of the Oath Keepers, an antigovernment group that pledges to support and defend its interpretation of the Constitution against all enemies.

The group, whose name comes from their original mission to disobey certain government orders, became a zealous supporter of former President Donald J. Trump, promoting conspiracy theories about “deep-state” cabals attempting to overthrow him and embracing his relentless lies that the 2020 election was illegitimate.

Mr. Durfee said he went to Washington in January to “stop the steal” and to protest against disproved claims of election fraud.

But he is more than just a fringe candidate mounting a long-shot race for the Legislature.

He also leads the Republican committee in the town where he lives, Northvale, underscoring the extent to which right-wing activism has become increasingly mainstream within the G.O.P., even in a Democratic stronghold like Bergen County, less than 30 miles from Manhattan.

The Oath Keepers, founded more than a decade ago, are known to draw members from the ranks of former military and law enforcement personnel. But records from the militia group, leaked after a database was hacked and shared with a group known as Distributed Denial of Secrets, have offered a new window into the organization’s links to active-duty police officers and government officials.

In New York City, Mayor Bill de Blasio has said that any officer associated with the Oath Keepers should be investigated — and fired.

Tuesday’s election in New Jersey features a matchup between Jack Ciattarelli, a Republican, and the Democratic incumbent, Philip D. Murphy, one of just two governor’s races in the country. All seats are also on the ballot in the state Legislature, where Democrats are expected to retain majority control.

Mr. Durfee — who gathered 165 signatures to get on the ballot and then ran unopposed in the primary — has called for ending all governmental oversight of parental rights, permitting families to use taxpayer-funded vouchers to pay for private and parochial schools, and cutting state agency budgets by 5 percent.

He has few illusions of outright victory.

“I’m an oxymoron in government,” he said. “I’m on the ballot because nobody challenged me. There’s that lack of participation among our citizens.”

He is running to represent a liberal area of northern New Jersey just across the Hudson River from New York. Registered Democrats in the district outnumber Republicans by more than three to one, making it difficult to find Republicans willing to invest the time and money to mount hard-to-win campaigns, party leaders said. (A frequent Republican candidate in the district, Dierdre Paul, called them “kamikaze races.”)

The county’s Republican chairman, Jack Zisa, defended Mr. Durfee as a “mild-mannered conservative,” but said that his main attribute was far more transactional: He was the only person willing to run.

“It’s a very tough district for Republicans and Mr. Durfee was, frankly, one of only a couple people who put his name in,” Mr. Zisa said.

Mr. Durfee is one of dozens of Oath Keepers across the country who are already in office or running for election, nearly all of them Republicans, according to a ProPublica analysis of the hacked database.

Roy Sokoloski, a Republican, was involved with recruiting candidates to run for office when he was a councilman in Northvale, a 5,000-person town on the northern border with New York State. He and Mr. Durfee worship at the same Roman Catholic church.

“If you don’t know his political background, he’s a nice fellow,” said Mr. Sokoloski, an architect.

But he believes Mr. Durfee’s candidacy is an ominous sign for a once-formidable party struggling to remain relevant in a state with nearly 1.1 million more registered Democrats than Republicans.

“He’s the worst candidate that the Republicans could have endorsed,” said Mr. Sokoloski, who said he voted against Mr. Trump twice and spoke wistfully of a time when G.O.P. leaders focused on issues like high taxes, not overturning elections.

“If the Republican Party can only find people like that,” he said, “what does that say about the party?”

Mr. Durfee said he drove from New Jersey on Jan. 6 to help with an Oath Keeper security detail. “We weren’t enforcers,” Mr. Durfee said. “We were just there as eyes.”

He said he was close enough to the chaos to get doused with pepper spray, but far enough away to avoid being swept into the crowd that rampaged through the Capitol.

Brian D. Sicknick, a Capitol Police officer who grew up in New Jersey and faced off against the angry mob, died after suffering what a medical examiner ruled were multiple strokes.

“It just morphed into something and got out of control,” Mr. Durfee said. “It’s just shameful.”

A devotee of the libertarian Ron Paul, Mr. Durfee speaks openly about his involvement with the Oath Keepers, which he said he joined in 2009, the year it was founded following the election of Barack Obama.

Mr. Durfee runs the Oath Keepers’ northern New Jersey operation and said he was responsible for maintaining the national group’s email and membership lists, which were included in the documents that were hacked.

His campaign, he said, has consisted mainly of attending community events, handing out business cards and directing people to a candidate website he built.

He has little money to spend in his race against the Democratic Assembly candidates, Shama A. Haider and Ellen J. Park. He and two other candidates running on the Republican line for the Legislature have reported that, as a group, they do not expect to spend more than $15,800.

He has not gotten support from the state Republican Party, and Mr. Ciattarelli has tried to distance himself from Mr. Durfee. “Anyone who advocates terrorism, or had anything to do with the insurrection, has no place in our party,” said Chris Russell, a strategist for the Ciattarelli campaign.

Mr. Durfee said he preferred to keep his savings in precious metals based on a worry that paper “fiat money” will eventually be devalued.

“I have dollars for my wife — we all have to live,” he said. “But I save in silver and gold.”

He spent two years in the Marines in noncombat roles. After earning his G.E.D., he took classes in computer programming at Chubb Institute. Last year, he lost a race for Northvale councilman.

A grandfather of three who opposes abortion, he is an ardent Catholic and a fourth-degree member of the Knights of Columbus, a rank given for patriotism.

“I’m not this ogre that’s hiding behind the fence — ‘Oh, here comes one of them Democrats. Let’s jump on them,’” he said.

Mr. Durfee participated in a videoconference with the Oath Keepers founder, Stewart Rhodes, and dozens of other members 10 days after the 2020 election, according to a leaked recording of the call released by Unicorn Riot, an alternative media site. As speakers discussed upcoming protests in Washington, Mr. Durfee can be heard urging people to “show the respect that we have for our country and our Constitution.”

“We’re not coming down there with fisticuffs, unless, you know,” he said, his voice trailing off.

“We’re all eager to be overzealous,” he added, “but we still have to maintain that position of respect for our flag and for our country.”

Instead, the violence that unfolded shook the nation, leading to the arrests of more than 600 people and a congressional investigation into what the F.B.I. has called domestic terrorism.

Assemblywoman Valerie Vainieri Huttle, a Democrat who represents Mr. Durfee’s district, said she saw his candidacy mainly as an indicator of Mr. Trump’s grip on the Republican Party, even in liberal bastions like Bergen County.

Republican strongholds still exist in New Jersey, especially in the rural northwest and along the Jersey Shore; Mr. Trump lost to Joseph R. Biden Jr. statewide by 16 percentage points, yet beat him in Ocean County by 29 points.

Still, Ms. Huttle said she was surprised to see such a far-right candidate vying for a seat she has held for 15 years.

“I would understand it in South Jersey,” said Ms. Huttle, who lost a primary race for State Senate and will be leaving the Legislature in January. “I don’t understand it here.”

Mr. Zisa, the Republican chairman, said it would be inaccurate to read too much into Mr. Durfee’s candidacy.

“We’re the Republican Party,” he said. “We’re not the Oath Keeper party.”

Nonetheless, he is hoping to capitalize on the media interest in Mr. Durfee’s affiliation with the extremist group. If it boosts turnout, he said, it could result in spinoff value for Republican candidates in more competitive races.

“This might drive the Republican voter out,” Mr. Zisa said.