The obscene sight of Tory leadership candidates splashing out cash by the bucketload is just one of the head-clutching, this-can’t-be-happening unbelievables of this extraordinary time. Spaffing it up the wall doesn’t begin to express the revolting spectacle of wild tax cuts and eye-catching gimmicks from the same austerians who garrotted every public service. Theresa May is the biggest spender, spraying goodbye billions on mental health, schools, colleges and a zero-carbon pledge, while Philip Hammond’s Treasury declares it “immoral” to steal from the emergency no-deal fund. What does she care? She is taking her revenge on them all.

Who knows the dark recesses of her mind, this locked-in woman incapable of communication?

But if May wants revenge, she has the power to blow away all her obstructors, tormentors and detractors, all 80 European Research Groupers, all those who blocked her deal. Who knows the dark recesses of her mind, this locked-in woman incapable of communication? Although the Mail on Sunday report on her has a ring of plausibility. She will keep her Commons seat, she voted for Rory Stewart and she “privately vowed to thwart any attempt by Boris Johnson to take the UK out of the EU without a deal”. (Never mind that her mantra was “no deal is better than a bad deal”.)

Soon Johnson will be strapped into her straitjacket, his phantom pregnancy of a new deal over. Nigel Farage and the ERG leer threateningly as the no-deal abyss beckons, with the pandemonium of border blockages, shortages of fuel, food and medicines and an Irish border shutdown.

Parliament will prevent it, one way or another: the Speaker, John Bercow, guarantees it. Only 10 brave Tory MPs voted for Jeremy Corbyn’s motion last week to block no deal. But in October, on the brink of no deal, when Labour calls a vote of no confidence to bring down the Johnson government, many more Tories will join them – the likes of Philip Hammond, David Gauke, Amber Rudd and others now in government including, it is suggested, May herself, will bring the final curtain down on their own party. Justine Greening, one of the brave, reckons as many as 50 would do the deed. Dominic Grieve says it would only need about six, and he has those. A question hangs over the disgraceful 21 Labour MPs who voted or abstained to permit no deal last week: surely they would vote no confidence in Johnson?

May, looking for a legacy before her 24 July departure, must be asking herself this: if she would bring down a Tory government to save her country, why not take action sooner? She has the power. She could press the nuclear option and revoke article 50, ending the Brexit trauma at a stroke: quite a legacy.

But the outrage would be terrifying, with leavers now more furious at denial of their democratic vote than about leaving the EU. So instead she could put her own referendum bill before parliament. Greening suggests a ranking of three preferences – no deal, May’s deal, or remain. May can say with conviction that too much is being decided behind closed doors by a tiny Tory electorate: democracy demands the people, not the Tory party, decide what comes next. She would, the Tory rebels think, get it through parliament quite easily, forcing the winner of this leadership charade to give the people the final say. That might even be a relief.

Remainers might well lose the referendum – people might choose no deal. But so be it, they will at least know the price. Last time, no deal was never even mentioned.

Johnson could grab the initiative, calling a snap election in full victory bounce before his unicorn Brexit plan is exposed, before Farage can claim “betrayal”. But how much better if May obliged him to call a referendum too. Tories are selecting him as their best hope to stop votes leaching to Farage, but analyst of Tory fortunes Tim Bale warns that he may not do well with the rest of the electorate. The “Boris brand” – Heineken man, who used to reach across party divides – morphed when he turned hard Brexiteer in 2016 – anti-immigration, lying about 80 million Turks and fibbing on NHS funds. Now he reaches mainly his own kind, and Farage will be warning that Johnson can never be trusted, and only the Brexit party will keep him straight. That fear has started Tory donors in secret talks for a Tory-Farage electoral pact, claims the Telegraph: Tories would stand aside for Brexit candidates in northern towns.

That should frighten the life out of Labour: the Tory-Brexit party split is Labour’s route to power. At a crucial shadow cabinet meeting tomorrow, Keir Starmer, Tom Watson, Andy McDonald, Emily Thornberry and many others will press hard for Labour to get off the fence, with full-throated backing for a referendum and remain. Skewered in recent elections for facing both ways, Labour needs to interrupt this Tory leadership parade of Brexiteers. The absence of the opposition making the remain case has left a gaping democratic deficit.

Could Corbyn pivot at this point? Easily, say shadow cabinet remainers, because there is no chance for a Labour-negotiated Brexit now: the only place to be is strongly pro-Europe. Labour members and voters are tearing their hair out at the party’s empty chair as the nation’s fate is decided by a handful of Tories.

If Johnson and Farage did make a pact, then in this Brexit crisis Labour must ally with Greens, Lib Dems and independents, promising electoral reform so it never need be done again. Sharing out seats is agonising – but this would be a national emergency to save the country from a Farage-Johnson no-deal government. The country will never have needed Labour more.

• Polly Toynbee is a Guardian columnist