Boris Johnson is ending his despicable campaign with a “blitz” through Labour seats from Grimsby to Wrexham. Listen with fear to his message: he has distilled it down to pure Faragism, reprising the spirit of Vote Leave’s “breaking point” poster and “70m Turks”. His party’s veins flow with Brexit party poison.

In erstwhile Labour-land, Brexit is the tin-opener that gives Conservatives a chance, not with dog-whistle but foghorn. That old populist template casting honest working people as being deceived by “the elite” echoes down the centuries from the far right. Already hard-pressed seats suffer from 10 years of lost public jobs, investment and services, yet Johnson urges them to blame not entitled Etonians but Jeremy Corbyn’s “great betrayal orchestrated from Islington by politicians who sneer at your values and ignore your votes”.

When the economy tanks due to his Brexit blunders he will distract attention on to foreign “enemies”

This old script worked for Mussolini as for Brazil’s Bolsonaro. It worked for Donald Trump, and, across Europe, for Silvio Berlusconi, Matteo Salvini, Viktor Orbán and Jarosław Kaczyński. Never mind if the messengers are hyper-elite metropolitans or kleptocrat billionaires: the trick works because they all use the same tin-opener – gut nativist “build the wall”, us-and-them fear of foreigners. The EU stands for that foreigner in Johnson’s refrain: “End uncontrolled and unlimited immigration from the EU, take back control from an unelected elite in Brussels.” He tells Sky News he will no longer let EU migrants “treat the UK as if it’s part of their country” – a sinister threat.

If the UK gives him a majority, let no one pretend they didn’t know what he was about. The music is so familiar, we recognise these old Enoch Powell tunes. If some shrug it off as what politicians say to get elected, it’s not. Powell was thrown out of his party, too out of step; yet Johnson has expelled those who won’t sign up to his new Powellism.

The short and vague Tory manifesto may make some believe that, beyond Brexit, they will act like traditional Tories. Johnson’s hard-hearted refusal to express pity for a child forced to sleep on a hospital floor is just normal Toryism. But think again, for this is no laissez-faire prospectus. Turn to the section on page 48, Protect our Democracy, sinuous and dark in tone: “One of the strengths of the UK’s constitution is its ability to evolve – as times have changed, so have parliament, government and the judiciary.” What kind of “evolution”? One that suits Tory electoral interests: gerrymandering boundaries, rejecting proportional representation and making it harder for non-Tories to vote. Poorer renters and students on the move, those without passports or driving licences, will be deterred by needing ID at polling stations. Curbing postal votes harms Labour voters most. Expats will get the vote, but long-resident tax-paying EU citizens are denied.

Here’s the threat: “After Brexit we also need to look at the broader aspects of our constitution,” the manifesto says, to “update the Human Rights Act and administrative law to ensure that there is a proper balance between the rights of individuals, our vital national security and effective government”. That “updating” means leaving the European convention on human rights, us alone with Belarus. Johnson, free from those restrictions, will unpick “the relationship between the government, parliament and the courts; the functioning of the royal prerogative; the role of the House of Lords; and access to justice for ordinary people”. Judicial review, the citizen’s guarantee against overmighty government, will be stopped from being “abused to conduct politics by another means”.

Be very afraid, as Johnson takes revenge on the legal system, on remainers, on human rights and on any democratic aggravations that stand in his way. We saw how fast his people moved to threaten to “review” Channel 4’s licence when it empty-chaired him for refusing its climate debate. Ofcom backed C4: what price will it pay?

The BBC expects the worst after Johnson’s assault yesterday on the licence fee. His constitutional review is a dire prospect from the man who illegally shut down parliament for five weeks. Reviewing “the functioning of the royal prerogative” would be to grant himself more of those arbitrary powers.

The Queen is useless as protection because she is unelected – elected presidents with written constitutions defend against government diktat – so she can only uphold whatever an elected parliament ordains. And expect no restraint from within his party. Johnson expelled all defenders of rights: instead we have Dominic Raab, Priti Patel, Liz Truss – his cabinet of horrors – with every MP blood-sworn to him personally.

Whoever wins this week, the Tories should worry about their future | John Harris Read more

Some think the failure of Corbyn to instantly expel all leftist purveyors of antisemitic filth would normally be a reason to deny Labour a vote. But these are not normal times. Behind the jovial bluster, Johnson is the greatest threat seen in our lifetimes. When the economy tanks due to his Brexit blunders he will do what the far right always does, distracting attention on to foreign “enemies”, using crude racism and attacks on “elite” judges, civil servants or any upholder of rights.

Every Labour campaign is labelled by Tories as a national “danger” – even Tony Blair in 1997 faced “New Labour, New Danger” posters. There was no “danger” but much hope in John McDonnell’s “first 100 days” plan set out yesterday: the only risk is to the wealth of those who did spectacularly well in this stagnant decade. However, there is no chance of a Labour majority, or of imposing reckless legislation without consultation as majority governments do. Far better, in plural societies, for a minority government to work with progressive parties, obliged to consult and agree.

The real bone-chilling danger comes from the impulsive, dictatorial, egotistical, absolute power of Boris Johnson unchained. But if every anti-Johnson, anti-Brexiter votes tactically against him, he can still be stopped.

• Polly Toynbee is a Guardian columnist