You know what you’re supposed to think of Boris Johnson. He is a cynical joker, a blond wrecking ball spouting Latin, an overprivileged preposteropath. He is a politician to be opposed fiercely, yet never taken seriously.

Look at the tools with which journalists are covering his leadership campaign. Dollops of scepticism about his Brexit plans, a few questions about that dodgy past – and a vast yawning incuriosity about any of his other policies. You can see why that is: when one has a star so box office and a show as dramatic as Britain crashing out of Europe within a few months, then who cares about the support acts? Especially if one doubts the Bullingdon buffoon is even capable of having policies. Still, this is an astonishingly easy ride to give a man probably just three weeks away from becoming our next prime minister.

It also hugely underestimates the former foreign secretary and the seriousness of the threat he now poses to our way of life. The area that has given me most pause over the past few days is the one that many of my colleagues have greeted with the greatest derision: Johnson’s outlining of his economic plans. I see their absurdity, yet they do not make me laugh. Are they ridiculous? No doubt. Reckless? Of course. But could they help him secure power and forever alter Britain? Sadly, I believe they could.

Theresa May's would-be replacement has found not just one magic money tree, but a whole forest

On early showing, Boris-onomics may be rife with intellectual contradictions, but politically it is utterly cogent – and the Tory hard right no longer seeks starred firsts, but state power. What they are putting together is a package both to buy enough of a public mandate for a no-deal Brexit, and then to rip up what remains of Britain’s tattered social contract between workers, employers and the state. More worryingly, I cannot yet see anything like a sufficient response either from the Labour opposition or among the disparate groups that claim to speak for remain.

What is the big difference between Johnson’s economics and that practised by his former colleagues in government? In a word, cash – and lots of it. In the 2017 general election, Theresa May famously told a struggling nurse that there was no “magic money tree” to give her a pay rise. Her would-be replacement has found not just one tree, but a whole forest. Pay rises for public-sector workers! Fewer workers paying national insurance! Tax cuts for the rich! And that’s just for starters.

As mayor of London, Johnson was mad about infrastructure, never happier than when strapped into a hard hat. He spaffed tens of millions on a garden bridge across the Thames and dreamed of erecting an airport on an estuary island. If he becomes prime minister, he will almost certainly unleash the biggest public-works programme seen this decade. You can imagine him now, performing Churchill to the BBC’s Laura Kuenssberg and her camera operator on building sites across the country; or driving a crane while reciting Tacitus. High-speed rail and superfast broadband everywhere! Nuclear power stations! Airport runways! Much of this could be announced as soon as an emergency budget in September, since his team say they want the economy “going gangbusters” by 31 October, just as the government bellyflops out of the EU.

Ah, you may say. Ah, but those are just more promises from the man who paraded himself in front of a lying bus. True, except every one of the serious contenders for the Tory leadership carried their own huge blank cheque. The last challenger standing, the supposed moderate Jeremy Hunt, has actually pledged greater spending commitments than Johnson. And, little noticed at Westminster, Nigel Farage this week made his first policy pledge for the Brexit party: a £200bn bung for everywhere outside London.

This tells you two things. First, that the two figureheads of no-deal politics, Farage and Johnson, are now in an open bidding war to buy up the Labour leave constituencies. Johnson is pitching himself as the Tory who can see off Farage and Jeremy Corbyn: he will keep on promising to spend public millions to keep his party in government. And he may have some success: polling from January this year showed that only 36% of Labour leave voters list Brexit as a top-three issue for them or their families. Far higher rank the economy, austerity and welfare cuts.

Second, that four years after Corbyn made Labour an anti-cuts party, Britain is finally entering a post-austerity era. After nearly a decade of teaching assistants resorting to food banks, of council services getting cut to the bone, and of homeless people lining our streets, the contrast will be so sharp as to be painful. When Ramsay MacDonald’s government finally devalued the pound in 1931 and the much-foretold chaos didn’t break out, a Labour stalwart remarked in bewilderment: “Nobody told us we could do that.” And when Britain finally breaks with austerity, there will settle over Whitehall and town halls across the country a similar stunned amazement. But the big lesson from this is that there is no longer a market for the language of “tough choices” and “there’s no money left”.

Will this stabilise a country in freefall from a hard Brexit or no deal at all? Of course not. The latest figures from the consultancy EY show that foreign direct investment into Britain is already plunging, a trend that will surely continue after Brexit. Whatever the Conservatives spend on Sunderland will dwindle into insignificance on the day Nissan finally follows Honda and Ford and announces it will halve the size of its plant there.

Yet Westminster has spent years ignoring the crisis of capitalism, by bunging money at large corporations and the rich. What you can expect under Johnson is a much bigger and bolder version of this traditional Tory move – which will be hallelujahed by the rightwing press, even as it sharpens inequality between rich and poor and between regions. However malign the motives and however grotesque the result, it will be aimed at buying time for a clapped-out party and their wealth-extracting mates.

Compare that with the alternatives, though. The ineffective People’s Vote campaign, with its promise of £4.7bn for “left-behind” (a terrible term) areas. Or Corbyn’s Labour, whose anti-austerity offering will struggle to stand out against a spend-happy Tory government. The opposition may claim that the Conservatives have stolen their policies, but politics isn’t literature: it places little value on originality.

The left can’t expect that pointing out Johnson’s racism or his past will sway voters – those tactics didn’t stop him grabbing City Hall. Remainers can’t carry on pointing out the madness of leaving the EU to turn this country into Singapore with jumpers – that didn’t work in 2016. We need to get much more serious and imaginative, show that staying in the EU is the best way to end austerity, and come up with policies to improve living standards here and now.

• Aditya Chakrabortty is a Guardian columnist