Michael T. Flynn, White House national security adviser-designate and retired three-star U.S. Army general, stands in the elevator at the Trump Tower in New York. (John Angelillo/Bloomberg)

The child exploitation conspiracy that apparently inspired a North Carolina man to show up in Washington this week with an assault rifle ranks among the most insidious fabrications to have spread online during the presidential campaign.

But it has at least two prominent backers on President-elect Donald Trump’s transition team: designated national security adviser Michael T. Flynn and his son Michael G. Flynn.

The retired three-star U.S. Army general and his 33-year-old son — who serves as his father’s chief of staff — have used their social media accounts to promote numerous baseless claims, including that members of Hillary Clinton’s campaign were implicated in a child prostitution ring.

The Flynns’ involvement in spreading this toxic allegation seemed mainly to serve as a disheartening example of the public’s susceptibility to ma­nipu­la­tion in the digital age, until a gunman arrived in northwest Washington on Sunday carrying an assault weapon and, according to authorities, planning to investigate the fictitious crime.

The gunman was arrested but not before he had fired at least one round, had caused panic at a pizza restaurant that had the misfortune of being linked to the anti-Clinton conspiracy, and had caused a busy stretch of Connecticut Avenue to be cordoned off by police.

President-elect Donald Trump named retired Lt. Gen. Michael Flynn his national security adviser on Nov. 18, but Flynn has a history of making incendiary and Islamophobic statements that have drawn criticism from his military peers. (Peter Stevenson/The Washington Post)

The elder Flynn, who served as Director of the Defense Intelligence Agency before he was pushed out by the Obama administration in 2014, called attention to the phony story just days before the election last month with a breathless posting on Twitter: “U decide - NYPD Blows Whistle on New Hillary Emails: Money Laundering, Sex Crimes w Children, etc...MUST READ!”

Hours after the gunman was apprehended, the younger Flynn renewed his support for the lie.

“Until #Pizzagate proven to be false, it’ll remain a story,” Michael G. Flynn said on Twitter late Sunday evening. “The left seems to forget #PodestaEmails and the many ‘coincidences’ tied to it.”

Younger Flynn’s tweet appeared to be a reference to unfounded allegations spread online that the Comet Ping Pong restaurant in Washington served as a front for human trafficking and sex crimes, and that hacked Clinton emails were riddled with coded references to kidnapping, molestation and child prostitution. The elder Flynn did not make the connection to the restaurant, though he has also never backed away from the claim that the Clintons were linked to a child sex ring.

Neither Flynn responded to requests for comment Monday. As designated national security adviser, the senior Flynn is poised to be among the most influential occupants of the Trump White House.

His son has appeared in photos with his father greeting other senior national security applicants at Trump Tower — where Trump and his transition team are based. The younger Flynn has no national security of significant government experience. One family associate said that Michael G. Flynn’s prior work experience included a stint working for an uncle's printing company in California.

The two were often separated during the elder Flynn’s military career, which included long deployments in Afghanistan and Iraq. The father even missed his son’s wedding while overseas.

But the two have been largely inseparable since Flynn left the military and echoed one another’s strident postings online. When the older Flynn launched an intelligence consulting firm, he gave his son a job as chief of staff.

The son traveled with his father to Moscow last year, according to family associates, where his father was seated beside Russian President Vladi­mir Putin at a gala thrown by RT, the Kremlin-controlled propaganda news outlet.

The older Flynn has gone largely quiet on social media since the election, but his son remains an active online presence. His Facebook account was updated Monday with a fresh link to a broadcast by right-wing provocateur Alex Jones.

Previous postings include a digitally manipulated image of Trump surrounded by handguns aimed at his head. The weapons are marked labeled with brands of major news organizations, including CBS, the New York Times and the Washington Post.

Neither Flynn appears to have been involved in the initial fabrication of the Clinton email claims. But both amplified the falsehood online as part of a broad stream of dubious postings and claims.

Multiple organizations with alt-right affiliations have spread stories accusing the Clintons of being tied to cases of human trafficking and sex crimes. One involves Comet Ping Pong, and another involves billionaire donor and convicted pedophile Jeffrey Epstein’s ties to the Clintons.

After leaving office, Bill Clinton was occasionally a passenger on aircraft owned by Epstein, who was also a regular visitor to Trump’s Mar-a-Lago estate in Florida.

The initial tweet by the older Flynn linked to an article from the far-right website True Pundit that points to the Epstein case. Comet Ping Pong is not referenced by True Pundit — either explicitly or implicitly. And in fact, the Reddit posting that spawned what’s come to be known as “PizzaGate” (the thread has been taken down by Reddit) is from Nov. 4, according to Snopes — two days after the True Pundit article posted Nov. 2.

Both Flynns have trafficked in these kinds of bogus stories many times before. The son has also pushed a conspiracy theory that Sen. Marco Rubio was a closeted homosexual who abused cocaine, and promoted baseless accounts that Hillary Clinton aide Huma Abedin had ties to the Muslim Brotherhood.

Aaron Blake and Julie Tate contributed to this report.