In the right-wing campaign to discredit the truth, every day brings a new low. I don’t mean Roy Moore’s campaign for the United States Senate, although that certainly has been at the centre, lately, of the broader crusade.

No, I mean the insidious drive — led, sadly, by Donald Trump — to undermine the reality-based media in America and in so doing to eat away at the underpinnings of our democracy: a shared basis in credible, verifiable facts.

Breitbart News, as that pro-Trump propaganda machine calls itself, was part of the campaign when it sent staffers — I will not call them reporters — to Alabama for the express purpose of knocking down a Washington Post story. In it, multiple women agreed to use their real names and to be quoted about Moore’s alleged sexual misconduct or assault when they were girls. (Breitbart ended up confirming the Post’s story but crowed about its own non-findings anyway.)

Trump was part of the campaign when he called this week for a trophy to be given for “fake news”, disparaging CNN in particular. And again when he reportedly cast doubt on the validity of the infamous “Access Hollywood” tape in which he bragged about grabbing women’s genitals. There is no question as to the tape’s authenticity.

But the new low came on Monday as Project Veritas — could its name be any more Orwellian? — was exposed for its clumsy effort to lure the Post into publishing a false story about a woman whose girlhood affair with Moore led to an abortion.

This would-be scam won the race to the bottom, so far, because at its black heart it mocked the bravery of women telling their own true, painful experiences. It tried to make a brazen lie the reason the women’s stories would be dismissed.

Happily, the Post’s reporting was rigorous. And, luckily, the scheme had all the savvy of a bully who tries to steal your lunch with the principal watching.

“Beyond boneheaded” was the characterisation of Byron York, chief political correspondent for the Washington Examiner, aptly noting that stupidity and malice are a bad combination.

A win, then, for reality. But a troubling question arises: who will be believed? Journalists and many thoughtful citizens may have been high-fiving on Monday. And for good reason: the Post’s video of the encounter with the would-be source was like a masterclass in reporting as high-wire act.

But Project Veritas quickly turned this into a fundraising opportunity for itself, claiming victory and releasing a video that purported to show the Post’s bias against Trump. (It depicted a Post reporter explaining the difference between news-side reporting and editorial-page opinion, which has been openly critical of the administration.) Some, undoubtedly, believed Project Veritas’s take, cheered and opened their wallets.

Are we as a nation so deep into our social-media bubbles and echo chambers that many have lost track of what’s real and what’s fake?

It is a deeply troubling problem, but hardly a new one.

“If everybody always lies to you, the consequence is not that you believe the lies, but rather that nobody believes anything any longer,” wrote the German-born political theorist Hannah Arendt many decades ago.

“And with such a people you can then do what you please.”

That frightening change is happening in America, and at a shocking pace. But there are encouraging signs, too.

One is that the reality-based press — the phrase I prefer to mainstream media — has been forced to be ever more transparent in how it operates. No more can we hide behind a paternalistic idea that “we know best” or “it’s news when we say it’s news”.

Far greater journalistic transparency is required now. And we are seeing more of it.

When BuzzFeed made it clear, as it broke the news about US Representative John Conyers Jr’s sexual-harassment settlement, that its information came from the far-right media figure Mike Cernovich, it protected itself and helped its readers. When the Post clearly laid out how it got its original Moore story — that reporters found and persuaded women to tell their stories — it makes its journalism more bulletproof.

News people used to joke that readers should never be allowed to see how the sausage is made. Now we need to show that messy process as clearly as possible. Our very credibility depends on it.

Project Veritas prides itself on its ability to do just that — to go behind the carefully lit scenes of media and politics, and to show what’s really happening.

But its perversion of that mission was on ugly display this week.

As a nation tries to keep hold of what’s real, despite a gaslighting president and his corrupt media helpers, we need more of what’s working: rigorous, careful journalism and radical transparency.

• Margaret Sullivan is The Washington Post’s media columnist. Previously, she was The New York Times public editor, and the chief editor of The Buffalo News, her home-town paper