There is only one place the British prime minister, Boris Johnson, should be right now. That is in Dublin, the city that holds the key to somehow resolving the Irish backstop and averting a no-deal Brexit.

Instead, Johnson is blatantly campaigning in marginal seats and promising one-off election bribes to the NHS – in confident expectation of what he pledged to avoid, a no-deal Brexit and/or a general election. The bribes are trivial compared with what a no-deal Brexit would cost. This grotesque act of national self-harm was invented purely to win Johnson leadership of the Conservative party. He has won it. He has weasled out of pledges before. It is time he weasled out of this one.

The UK is now locked in a nonsense. Jeffrey Donaldson, chief whip of the Democratic Unionist party in Westminster, on whose goodwill Johnson wholly relies in the Commons, has dictated that “our bottom line is no hard border on the island of Ireland and no new border between Britain and Northern Ireland”. These are blatantly incompatible. You cannot both be in a customs union and outside it. They are mutually exclusive, and Donaldson and Johnson must both know it. Yet this incompatibility underpins the UK’s whole future as a trading nation. The only conceivable way through is some fudge to define “hard border” as somehow a soft one. It must still be a border, but at least some verbal compromise might kick the can down the road.

The compromise can come from only one quarter, Ireland’s prime minister, Leo Varadkar. Yet Johnson has not had the guts to meet him. He has talked twice with his friend Donald Trump. He has electioneered around the Celtic fringe and northern constituencies. He has not even begun to negotiate to avert no deal, which he once claimed was his priority. Was he lying? Is his cynicism total? Only Varadkar can reassure the 27 EU states that a transitional UK withdrawal agreement is feasible. He and Johnson must do a deal, and desperately soon.

The new Downing Street mastermind, Dominic Cummings, is reported to believe his boss can use a general election to neutralise parliamentary opposition to no deal through September and October, and thus over the critical 31 October deadline. He thinks he can thus engineer both a no-deal Brexit and an election triumph for his boss. This is despite such a strategy involving an almost certainly gridlocked parliament, chaos on Britain’s borders and severe economic disruption.

Once upon a time we might have expected an independent parliament to summon MPs back to Westminster forthwith and put a stop to this absurdity. To this there is only one answer: what independent parliament? Britain’s supposed leaders are currently in the grip of two followers of Leon Trotsky – namely Cummings and Jeremy Corbyn’s chief strategist Seumas Milne.

The centre cannot hold. And meanwhile, a populist fever is raging through British politics.

• Simon Jenkins is a Guardian columnist