MERIDIAN, Idaho — The first time Alek Kyzik tweeted, two months ago, he invited Donald Trump Jr. to a pro-Trump rally he was hosting in Boise.

“I would love to chat,” he wrote in a public post on July 9 addressed to the president’s eldest son, who did not respond. “Thanks!”

The invitation was to a “cruise,” the type of provocative show of force that would become Kyzik’s signature: a motor-rumbling, flag-waving caravan of cars and trucks endorsing Trump on the streets of liberal cities. The most recent cruise he hosted involved thousands of vehicles advancing on Portland, Ore. It ended with one participant shot dead.

Kyzik was not well known in Republican activist circles. In fact, Kyzik was not even his real name, according to a review of business and academic records, as well as interviews with family members.

He is Alex Kuzmenko, a 33-year-old architect who lives in a second-story apartment in Meridian, a bedroom community outside the liberal-leaning city of Boise. His YouTube channel featured luxury car reviews before shifting to pro-Trump memes and videos several months ago. He and members of his family — immigrants from Belarus and Ukraine ­— had almost no political profile before organizing one of the most consequential pro-Trump demonstrations of the summer.

The shooting of Aaron “Jay” Danielson, 39, a supporter of the far-right group Patriot Prayer and a participant in the cruise rally, became a bloody bookend to an anguished summer in Portland and other communities. The alleged assailant, a self-described adherent of antifascism, or antifa, was later killed in an encounter with police.

The killings turned the cruise rally into a spectacle of American disorder. The episode elevated a tactic — proclaiming a political ideology with a parade of people revving their engines and openly displaying guns — that could add fuel to an increasingly bitter presidential contest.

As intelligence officials warn of foreign efforts to inflame divisions ahead of the Nov. 3 election, the work of Kuzmenko and his relatives, who organized the activities using online accounts that did not reveal their full names, shows how little-known individuals with no recorded history of political engagement can seize an outsize role in the campaign.

With little more than a Facebook log-in, private citizens have been able to tap into an existing appetite for protest and partisan faceoff. As with the teenage shooting suspect in Kenosha, Wis., and the black-clad protesters in Portland, street-level confrontations have become defining moments in the era of viral politics, at times eclipsing the official activities of Trump and his Democratic opponent, Joe Biden.

Kuzmenko, who declined to comment at length for this story, has said publicly that it was not his intention for cruise participants to confront protesters directly, or for the caravan to end in violence. The goal, his family members said in interviews, was simply to show support for the president.

But coverage of the caravan took on a life of its own, becoming fodder for conspiracy and propaganda outlets. The Epoch Times, a pro-Trump publication sympathetic to the Falun Gong spiritual movement critical of the Chinese government, featured Kuzmenko, referring to him by his alternate name, in its live coverage of the event on social media.

“MAGA is heading into Portland,” right-wing provocateur Jack Posobiec, a correspondent for the pro-Trump One America News, wrote on Twitter. The tweet was shared the next morning by Trump, who added, “GREAT PATRIOTS!”

Video of the cruise rally and its chaotic entry into downtown Portland was also promoted by the Kremlin-financed RT, along with lesser-known U.S.-based outlets seeking to improve relations with Moscow.

“Oregonians tired of riots organized a mass car rally in support of Donald Trump,” read the Russian caption on the video shared across Facebook by “The Russian American,” the media arm of a Seattle-based nongovernmental organization advocating improved ties with Moscow. No one from the group, the Russian-American Cooperation Initiative, took part in the caravan, said its director, Sergey Gladysh, declining to elaborate on why they had nonetheless amplified video of the event on social media.

Local GOP officials and activists said Kuzmenko and his relatives were strangers to them until they began organizing pro-Trump caravans this summer, first in Boise, where two occurred in July and August, and ultimately in Portland. “I attended one,” said Victor B. Miller IV, chairman of the Ada County Republican Central Committee in Idaho, declining to comment further.

Cin Alfonso, co-founder of the Idaho Liberty Dogs, a pro-Trump group that has sent armed civilians to monitor Black Lives Matter protests, had not heard of Kuzmenko before his cruise rallies this summer. “Alex just popped up one day,” Alfonso said.

Trump campaign spokesman Tim Murtaugh said that the campaign has had “no contact” with Kuzmenko and that it did not provide any Trump merchandise for the cruise rallies.

Kuzmenko and his family said they organized the Portland rally because of their enthusiastic support for Trump as well as concern about months of unrest there. “Nobody’s paying us to do any of this,” said one brother, Nikolay Kuzmenko. Another brother, Dennis Kuzmenko, said, “We wanted it to be organic.” Oleg Volkov, a Portland-based associate of the family who recorded video from the scene of the caravan, said he was “not affiliated with any groups or anything like that,” declining to comment further.

Despite the focus on the bloodshed in Portland, including in a volley of tweets from the president the morning after the Aug. 29 episode, little is known about the personalities who set the events in motion.

When approached at a church in Meridian run by a relative, Alex Kuzmenko said his political activities were personal, insisting, “I’m not a public figure.”

Nikolay Kuzmenko said the hosts did not reveal their full names because they feared backlash from antifa, a loose collection of left-wing activists Trump has made a focal point of his reelection campaign.

Alex Kuzmenko and most of the other rally organizers are members of an extended family that came to the United States in 1993 from near Chernobyl, Ukraine, multiple family members said. Alex Kuzmenko’s mother, Lyubov, said she is originally from Belarus.

In an interview outside her blue farmhouse in Nampa, Idaho, Lyubov Kuzmenko and her son Dennis traced their embrace of Trump to the family’s difficulties living under the Soviet system. They said the family suffered religious persecution because of their evangelical Christian beliefs and that relatives who stayed in Belarus have had little opportunity to prosper.

“Communism. That’s what we got away from,” said Dennis, 24, who owns a local heating and cooling company. “Trump is all about religious freedom and letting people serve their own God. And we’re behind that.”

The family first settled in Portland and then relocated to Meridian in 2006, the 24-year-old and his mother said. They chose to settle in Idaho’s Treasure Valley because of the family atmosphere and access to the outdoors, Lyubov Kuzmenko said. She and her relatives make up about half the congregation at the Fountain of Life Church, a local evangelical congregation that is led by a relative and holds services in Russian.

Alex Kuzmenko is listed as the director of a real estate company that advertises the opportunity to “Sell Your House For Fast Cash.” He and his wife, Lily, have run a wedding photography business. Several family members are listed as officers of freight shipping and trucking businesses, according to corporate records.

Dennis Kuzmenko said he and Alex conceived of hosting Trump rallies in Boise and Portland to fill a campaign void.

“There’s no Trump rallies going on. There’s nothing going on. Everyone’s just hiding out,” he said. “We wanted people to get out there.”

He added: “It was just fun for us.”

Almost all of the rally’s hosts used pseudonyms or variations of their names to host the Portland event on Facebook. Nikolay, who appears to operate multiple Facebook accounts, goes by Nik Kuz. Nikolay’s wife, Yuliya Kuzmenko, goes by Julie Kuz. Another host, Tina Berezhnoy, shortened her name to Tina Bere. Neither woman responded to requests for comment.

The Kuzmenko family has little documented history of political activism. Alex Kuzmenko voted in 2016 but in no other American election, records indicate. His brother Dennis, who said he is the only family member born in the United States, is also the only member of the Idaho family to make a contribution to a political committee, according to the Federal Election Commission database. It shows he gave $60 to a pro-Trump group and other Republican causes last year.

A Facebook co-host for Alex Kuzmenko’s first rally, Bonnie Isbill Dodson, said she had never met Kuzmenko or attended any of his rallies, including the one she co-hosted. The Meridian resident said she had been scrolling through items on Facebook Marketplace when she came across the invitation for the July rally in Boise and was alarmed by a string of offensive comments. When she contacted Kuzmenko, he asked her to monitor the posts. The next thing she knew, she said, she was listed as a co-organizer on the event page.

Kuzmenko publicly distanced himself from a subsequent Portland caravan, writing on Facebook: “Given all the circumstances and investigations going on, we would like to be VERY CLEAR that the Labor Day Portland Rally is NOT organized by us. Such events take time to organize and everything that is organized rapidly is simply NOT SAFE.”

He added, “Based on our law enforcement contacts, they highly discourage any rally from happening so soon after the first one.”

Kuzmenko has already tired of political activism, his family insists. “He wants out,” Dennis Kuzmenko said of his brother’s organizing efforts. “He wants someone else to take over.”

He continues to promote his past events, however. After warning against new rallies, he returned to his Facebook event page, which is followed by nearly 11,000 users, to draw attention to a highly produced video of the rally he had organized in Portland, highlighting the flag-waving spectacle before the street-level brawls began. “The rally video is done, please like and share with friends and family,” he wrote on Sept. 5.

The video has been viewed about 150,000 times, drawing considerable attention to his YouTube channel, called “Open N Review,” which was devoted to luxury vehicles for two years before a sudden shift to pro-Trump politics this summer. His videos used to average about 10,000 views. Now he is topping 100,000, and a YouTube spokeswoman, Charlotte Smith, confirmed that his channel is earning revenue from ads appearing on his videos.

Most of the video’s engagement on Facebook, according to data from the analysis tool CrowdTangle, came from a post in a group called “Pray for Our President” by an account called “Nozul Olyvia,” its profile picture an image of the Rev. Martin Luther King Jr. Facebook removed the account following questions from The Washington Post. It was not clear who was behind the account, with a Facebook spokeswoman, Sarah Pollack, saying only that it violated the company’s policy on authenticity.

In drumming up online interest in the rallies, Kuzmenko and his family showed considerable sophistication on social media, including hiring a Boise-based video company to polish his presentation, according to the head of the company, Bryan Bowermaster. Kuzmenko’s first action on the event page was provocative — sharing a Facebook post from the president that included a video showing him running for office indefinitely, with signs reading “Trump 2024” and on into the future. The same message was later echoed at the August rally in Portland, with chants of “12 more years, not just four!”

“We call all patriots and God-loving Americans to stop waiting for a change, but be the change in your country by praying and voting, in person, this November,” Kuzmenko said, reading from notes into a megaphone at the rally.

In the weeks leading up to the Portland cruise, he and his relatives also posted repeatedly about opportunities to purchase flags and other gear for the event. American flags and Trump flags went for $5 to $15, while the price for “thin blue line” flags was $10, according to screenshots of their various advertising announcements on social media. Kuzmenko’s sister-in-law, who goes by Julie on Facebook, offered “CUSTOM MADE” hitch mounts, capable of holding up to three flags, at $60 apiece.

The caravan route was apparently intended to avoid downtown Portland, the site of months of nightly and often violent clashes between law enforcement and protesters. But some participants drove there anyway, firing pepper spray and paintball guns.

“The shooting was not part of the event. It was not part of the cruise rally,” Kuzmenko said in a video, accusing antifa of funneling people downtown.

In a three-hour video of the early phase of the cruise rally, uploaded to Kuzmenko’s YouTube channel, a woman who appears to be holding the camera says at one point, “We’re going to head over to downtown Portland.”

At another point, the woman behind the camera — who switches seamlessly between English and Ukrainian — seeks to stage Internet-ready enthusiasm, asking a rallygoer standing before a crowd to begin a chant: “Can you walk up and down the line, like, ‘USA?’ ”

CORRECTION: This article has been updated to correct the partisan makeup of Boise. Although the city leans liberal, and mainly elects Democrats to the state legislature, the greatest number of voters are unaffiliated.

Wolf reported from Meridian. David L. Stern in Kyiv and Julie Tate, Alice Crites, Ellen Nakashima and Shane Harris in Washington contributed to this report.