Duluth, Minnesota CNN  — 

Prior to the first Presidential debate, a baseless conspiracy theory inundated many Americans. The Trump campaign, Fox News, and a slew of Trump-supporting Facebook pages all fueled speculation that Democratic presidential candidate Joe Biden might wear a secret earpiece to assist him in his debate against President Trump.

“I thought Biden had somebody in his ear,” said one Trump supporter the morning after the first presidential debate. Her belief was shored up, she said, by video she had viewed of Biden supposedly adjusting a wire during the debate.

She was on her way to a Trump rally in Duluth, Minnesota and was referring to a YouTube video she was sent by a friend who is serving with the military overseas.

In fact, the video does not show Biden wearing a wire; it shows a crease briefly forming on Biden’s shirt after he reached into his coat to itch his shoulder. But when false evidence emerged to support the baseless earpiece claim, it took off like wildfire.

One version of the video that was flagged by fact-checkers as false on Facebook had been shared more than 22,000 times and viewed 800,000 times by Thursday night.

Alan Duke, the editor-in-chief of Lead Stories, a fact-checking company that works with Facebook, said his team flagged hundreds of videos and images making false earpiece claims. He said it was one of the most widespread false narratives his team had handled this year — and that was, he added, “in a year of massive false narratives.”

The earpiece conspiracy theory devolved even further, Duke said, and on Wednesday his team had to flag as false claims that Biden had an IV during the debate.

While many versions of the wire video on Facebook were prominently labeled with fact-checks, the YouTube video that was viewed by the woman attending the rally in Duluth was still live on Thursday night with more than 48,000 views and no fact-check. The video also circulated on Twitter, and one version alone had 4 million views by Thursday night.

Ivy Choi, a YouTube spokesperson, said the video did not violate its policies. The company said it was linking to fact checks at the top of searches for queries like “Joe Biden wire.”

However, the woman in Duluth who showed CNN the video had been sent the video directly by a friend. This means she wouldn’t have seen the factcheck, as YouTube is only labeling searches, not individual videos.

Twitter said the video didn’t break its rules and gave no further explanation.

Andy Stone, a Facebook spokesperson, said it had fact-checked the video but would not be removing it.

Just as many conservatives believe that Silicon Valley and mainstream media are biased against them — that mistrust extends to Facebook’s fact-checkers, too.

Supporters at two Trump rallies in Minnesota over the past few weeks told CNN that posts they share on Facebook are sometimes labeled as false, but they don’t believe the fact-checkers.

When told that the video was fact-checked and found to be false — that what looked briefly like a wire was instead a wrinkle in Biden’s shirt — the Duluth rally attendee appeared to reject the judgment of the fact-checker.

“You’re talking about Joe Biden, you think his shirt isn’t pressed perfectly?” she asked.