One of the most-loved, least-supported narratives in conservative media is that many protesters who demonstrate against President-elect Donald Trump are paid to do so — meaning they don't really represent organic opposition and are nothing more than cash-grabbing, millennial mercenaries.

So it was more than a little surprising to see a thorough debunking of a paid protester myth on Fox News, of all places, Tuesday night.

In just his second week anchoring the 9 p.m. time slot that previously belonged to Megyn Kelly, Tucker Carlson dressed down the creator of a hoax website that purported to offer professional protesters $2,500 monthly retainers and $50 per hour, plus health, vision and dental insurance.

"On your website, you claim that you pay a retainer to 1,817 operatives every month," Carlson said, confronting the site's creator, who goes by the assumed name Dom Tullipso. "Now, if that were actually true, that's $54 million a year you're spending just on retainers. It's over $30 million a year if you're paying them for six hours a week work. That's demonstrably — you're not doing that."

Indeed, the compensation claims made by Tullipso's fake company, Demand Protest, are so outlandish that they should have instantly raised red flags. Yet they attracted serious coverage from the Drudge Report, Washington Times, Gateway Pundit, Townhall and other conservative news outlets inclined to believe anything that aligns with their worldview.

"Is this an effort to discredit the protesters at the Trump inauguration?" Carlson asked Tullipso. "Is it an effort to convince conservative news organizations to pick up the story and therefore highlight their gullibility?"

Tullipso initially feigned defiance, insisting his company is legit, before breaking character to acknowledge the ruse.

"I mean, it's pretty darn easy these days to just say whatever the heck you want on national TV and have it pass off as truth," he said. "And, you know, it's pretty — I don't know, just pretty incredible to me how easy it was to get the coverage we got."

Tullipso's explanation sounded a lot like the one offered by Paul Horner, a fake news creator who told The Post in November that he made up a story about an anti-Trump protester being paid $3,500.

"His supporters were under the belief that people were getting paid to protest at their rallies, and that’s just insane," Horner said. "I've gone to Trump protests; trust me, no one needs to get paid to protest Trump. I just wanted to make fun of that insane belief, but it took off. They actually believed it."

What a sad commentary.

Tullipso ended his appearance on Carlson's show with this: "God bless you for fact-checking."

Amen. But Fox News has not always done such blessed work. Two days after the election, the network was taken in by a false claim that anti-Trump protesters were bused in to a rally in Austin and perhaps paid by liberal billionaire George Soros. The man who started the rumor later admitted to the New York Times that he simply tweeted a photo of several buses and connected them to the rally without any evidence; the buses actually transported attendees of a technology conference.

Fox News's morning show has repeatedly promoted the unproven idea that anti-Trump demonstrators are paid to rally for causes they actually don't care about, as if it is inconceivable that a historically unpopular incoming president has truly galvanized opponents.

Obviously some people who participate in protests work for — and are therefore paid by — liberal activist groups. Organizing rallies is kind of their job. But, as The Fix's Philip Bump wrote in November, "the idea that money pours into progressive groups so that they can hire folks to dispatch around the country lacks any grounding in reality."

Carlson, to his credit, took apart a notion that has been legitimized by his own network and which is surely popular among some of his viewers. It was a bold move — and hopefully a sign of things to come.