A confession: I tend not to read the online comments about anything I write for the Guardian. But as I am about to embark on a short “politics of mental health” speaking tour down under, I made an exception for the comments section beneath an interview I did for Guardian Australia. I am glad I did. For there were two comments so good they left me wishing I had written them myself. I shall certainly be using them in future.

I have no idea who sleuthfortruth is, but someone should find them and hire them as a speechwriter. “Voting for a populist party is like diving headfirst into an empty swimming pool, because you’re angry that there’s no water in it.” Brilliant. Trump and Brexit to a tee.

Trump: the inherited wealth billionaire who became president by ventilating and capitalising on public anger at politicians and elites, winning over many among the disaffected working classes, yet now pursuing policies aimed at further enriching the rich, and a politics of narcissism and family aggrandisement at the expense of the US’s global reputation.

Revealed: the rise and rise of populist rhetoric Read more

Brexit: won with the help of the votes of those who will be hardest hit by its impact, as every regional analysis has shown. Those votes were secured with arguments about sovereignty, economic strength, more money for the NHS, trade deals galore falling from trees, big falls in immigration – arguments that have faded and died as campaign-winning rhetoric has been exposed to the real world of EU negotiations, the law and parliamentary arithmetic. So now the populists are reduced to saying simply that Brexit must happen because people voted for it, and a likely incoming prime minister, to be elected by a majority of the less than 0.25% of the country with a say in the matter, happily parrots his support for a no-deal Brexit that he and everyone else said was not even an option three years ago.

When a few populists piled in on sleuthfortruth, they held their ground and added: “Populism is the art of agitating the disaffected voters to vote against their best interests, by amplifying problems and not really offering anything in return.” Trump, Salvini, Johnson, Farage: sleuthfortruth has your number.

Sleuthfortruth is a good name for the holder of such a viewpoint, for truth has been a prime casualty of the populist era. According to Washington Post factcheckers, Trump has averaged 12 misleading or outright false statements for every day of his presidency. Worse, he shows politicians around the world that – thus far – he can get away with it.

We are not just in a post-truth world, but a post-shame world. How else to explain that Boris Johnson once lost his job at the Times for lying, yet the same newspaper now endorses him to be prime minister?

The £350m a week that was promised for the NHS was post-truthery. The fact that Johnson is rarely challenged on it, and waves it away when he is, is post-shamery – his, politics’ and the media’s.

Populism means never having to say you’re sorry, and never having to say you’re wrong

We saw a vignette of the same kind of thing in Andrew Neil’s BBC interview with Johnson last Friday. Neil was pressing Johnson on whether his failure to back Kim Darroch in the ITV leadership debate a few days before was a factor in Darroch’s decision to resign as UK ambassador to the US (spoiler alert: it was). Johnson gave a version of events that was directly contradicted by the account Darroch had given to friends. He also – and well done to Neil for calling it out as a regular Johnson tactic – sought to deflect the question by answering one that hadn’t been asked, about the leaker. Post-truth and post-shame both take place in a world where, as chancers such as Johnson and Trump know, events move so fast that the caravan quickly moves on.

If our democracy was functioning well, there would be an opposition in the wings, a government-in-waiting, providing the answers and the solutions, the leadership and the strength in depth, that the government is failing to. But that is not happening, is it? In recent polls, Labour has been closer to single figures than the kind of support needed for a majority. Populism is not about being popular. It is the relegation of fact and reason to lies and emotion. The main point I made in my interview with Guardian Australia was that the populism of the right would not be defeated by populism of the left. Yet if I were to think of two words to sum up Labour’s handling of antisemitism, especially in recent days, post-truth and post-shame would be right up there.

Populism means never having to say you’re sorry, and never having to say you’re wrong, because you just say something different about something else. Take the latest policy announcement of the Brexit party. “The Brexit party will invest £200bn in the regions by scrapping HS2, halving the foreign aid budget, and refusing to pay Brussels £39bn,” it says.

There are so many unanswered questions in there it is hard to know where to start. “Refusing to pay £39bn” presumes that we are leaving the EU without a deal and preparing to break the law to do so. Do their calculations include any economic hit at all, or are we still fantasising that a no-deal exit can be managed without economic downside, even before the EU understandably decides that such an act of bad faith might merit some sort of retaliation?

The aid budget totals about £14bn, so scrapping half of it only gives you £7bn. And even if you assumed you could somehow get back to the Treasury the estimated £56bn cost of HS2, which you can’t, and even assuming there would be no economic costs of reversing the project, which there would, you still only have half of the £200bn promised in total. Post-truth, post-shame. I can see Nigel Farage laughing his head off: “Can you believe that Campbell has actually gone and tried to fact-check our ‘policy for the regions’ like it was serious?”

But this is not a policy at all. It is an attempt to pretend that they have one, so they can go around the country and say they care about the regions. It is a very empty swimming pool. Diving into it would be dangerous indeed.

The same goes for Johnson’s no deal – and, in some ways, even worse has been the sight of Jeremy Hunt, Matt Hancock, Amber Rudd, Damian Green and others pretending to share his view that no deal need not be, as they had previously argued, an unmitigated disaster. Jump in, the water’s … all gone.

• Alastair Campbell is an adviser to the People’s Vote campaign and editor-at-large of the New European. He is co-founder of Equality4MentalHealth