If you want to know why the worst president in US history currently stands a very good chance of winning again, consider a few facts. Donald Trump’s re-election campaign is already in full flow, brimming with cash, drenching social media with targeted ads, and reaping oceans of data on voters.

The impeachment drama is, predictably enough, the perfect opportunity to put out material that plays to the idea of Trump as a noble maverick, struggling against the liberal conspiracy implied by his online questionnaires: “Do you agree that President Trump has done nothing wrong? Do you believe the Democrats will try and make up LIES to impeach the president?”

The Democrats’ most likely challenger, by contrast, made headlines last year when he cut his online ad budget, and decided to concentrate on TV advertising: a very odd decision by Joe Biden, but there we are.

What really helps Trump is Facebook. Last October, it became clear that, whatever its collective remorse about the role it had played in Trump’s election three years before, Mark Zuckerberg’s company had quietly exempted advertising by parties and candidates from its regulations on truth and falsehood. After the flurry of criticism that followed, there was speculation that Facebook might shift – on both that policy, and the kind of micro-targeting of adverts that makes it almost impossible to scrutinise what a candidate is saying to voters, and why (the Trump campaign is currently reckoned to be launching more than 1,000 new micro-targeted Facebook ads every day).

But earlier this month there came confirmation that on these two crucial points, company policy was going to remain unchanged.

Cosmetically at least, some other internet giants have been tightening up. Not that it absolves Twitter of much of the blame for spreading hatred and misinformation – or indeed, hosting Trump’s personal feed – but in October last year it banned almost all political advertising. Again, Google is hardly free of responsibility for encouraging the worst kind of online politicking, but it has stopped political advertisers targeting people based on their political affiliation, and promised to take action against “demonstrably false claims”.

Facebook, by contrast, isn’t moving. It may have shone some light on political ads via new transparency tools, announced that users will now have the option of seeing fewer ads about “political and social issues”, and increased its efforts against foreign interference, but the most egregious aspect of the way it treats politics remains untouched.

When I contacted the company’s press office, I received an email from a global “CEO advisory firm” called Teneo that requested I paraphrase Facebook’s company line – that it is not its role to “referee” political debates and prevent politicians’ messages reaching their intended audience; and that targeted ads are considered a good thing not just by political campaigns, but charities and NGOs. Self-evidently, the problem with that defence is that it leaves candidates and campaigns free to lie with impunity, and micro-targeting makes doing so even more mouthwatering.

An example: in October last year, Trump’s organisation released an ad falsely alleging that Biden had offered the Ukrainian authorities $1bn if they dropped an investigation into a company linked to his son. CNN refused to air it; Facebook had no such qualms. There will be plenty more of this stuff.

Hypocrisy is at the heart of Facebook’s refusal to ban false political advertising | John Naughton Read more

It is interesting to note that Facebook’s hands-off approach to political lying has reportedly been endorsed by Peter Thiel, the Trump-backing billionaire who sits on Facebook’s board. If you want to understand the kind of thinking he supports, a good place to start is the recent leaked memo written by Andrew “Boz” Bosworth, Facebook’s “augmented and virtual reality vice-president”. Trump won three years ago, he says, because “he ran the single best digital ad campaign I’ve ever seen from any advertiser”, and this year Facebook’s ad policies “very well [sic] may lead to the same result”.

When it comes to the relevance of Facebook’s political ads policy to Trump’s chances, Bosworth goes all mystical. “I find myself thinking of the Lord of the Rings at this moment,” he says. “Specifically when Frodo offers the ring to Galadriel and she imagines using the power righteously, at first, but knows it will eventually corrupt her. As tempting as it is to use the tools available to us to change the outcome, I am confident we must never do that or we will become that which we fear.”

But what of the fact that Facebook’s algorithms privilege the most hysterical, mendacious, loathsome kind of political discourse? “The algorithms are primarily exposing the desires of humanity itself, for better or worse,” says Bosworth, going on to claim that “corporate paternalism” is not the answer, and that “giving people tools to make their own decisions is good, but trying to force decisions upon them rarely works (for them or for you)”. Facebook, in other words, just presents you with the poison, often in a micro-targeted form that makes it even more tempting: if you want to imbibe it, that’s up to you. In this vision, Tolkien-esque cod-philosophy is less relevant than reckless libertarianism. Such is the variety of corporate responsibility offered by arguably the most powerful corporation in the world.

The traditional media might still understand elections in terms of speeches, campaign launches and set-piece interviews. But as evidenced by Boris Johnson’s victory after weeks of eluding any meaningful scrutiny, this is not where politics really happens any more. Facebook offers a dual enticement to campaigns and candidates: you can spend no end of money spreading falsehoods, and also be assured that you are using the most effective means of political communication anyone has ever invented.

It hardly absolves Labour of its serial failures, but this formula was right at the heart of the Tory win in December: towards the end of the election, it was revealed that 88% of Conservative advertisements published on Facebook over a four-day period contained claims deemed to be misleading by Full Fact, a fact-checking organisation used by Facebook itself (the figure for Labour material was 7%).

Honourable debate might have symbolically breathed its last on the occasion in 2008 when Senator John McCain silenced an audience member at one of his rallies when she implied that Barack Obama was not American. There may well be chilling auguries of the future in the kind of facts pointed out last week by my colleague Emily Bell – that the Indian prime minister, Narendra Modi, an expert at internet politics, has never held a press conference, that the White House press secretary has not delivered a public briefing in six months – and, for that matter, that the new British government apparently wants precious little to do with mainstream news and current affairs programmes.

We are, it seems, in the opening stages of a completely new age, in which victory will usually go, as the New York Times put it the other day, to those who specialise in “emotionally charged, hyper-partisan content, regardless of its factual accuracy”, and very nasty techniques indeed: witness the 2016 Trump campaign targeting anti-Hillary Clinton material at black Democrat supporters via Facebook, so as to suppress turnout.

Something lodges itself in my head anew every time I write about Facebook: that even if it began with benign intentions, it has long since failed to match its power with the commensurate responsibility. After a fashion, Zuckerberg himself seems to agree that there is a case for action. “There are a number of areas where I believe governments establishing clearer rules would be helpful, including around elections, harmful content, privacy, and data portability,” he said in his recent new year message.

What is actually required is enforced break-up, tight subsequent regulation and the belated realisation that Facebook has come close to tearing democracy to pieces in the name of bringing people closer together – all thoughts now fashionable among people at the top of the Democratic party. Facebook’s unprecedented corporate power, however, offers an answer to that: the fact that Trump may well beat whichever Democrat is selected to challenge him, using all the shadowy sophistry Facebook puts at his disposal.

• John Harris is a Guardian columnist