The Conservatives have been in government for nine years, but Boris Johnson seems not to feel the weight of that incumbency. He is seeking his first national mandate as prime minister, so doesn’t see himself as a shop-soiled candidate. But he is asking voters to return his party to office for a third time, and it wasn’t much loved to begin with.

Labour has the opposite problem. There is plenty of hunger for a new direction in government, but the appetite is dulled by the sight of Jeremy Corbyn asking to be prime minister. It is risky to serve a dish that the electorate has sent back to the kitchen once already.

Both of the biggest parties are trying to sell messages of renewal with messengers who are familiar and unpopular. Polls give the Tories a head start, but there is wind behind the opposition in a campaign when even the government admits it is time for a change.

There will be ample talk of Brexit, but it will continue to be a proxy for grievances only tangentially connected to EU membership

Johnson’s claim to be the candidate for a fresh start is contained tenuously in his promise of a swift end to the Brexit saga. He would implement his deal and a burden would thus be lifted from the nation’s shoulders. The prime minister argues that Labour’s policy is to avoid having a policy, deferring the choice, prolonging the pain, which is true enough. The brighter the spotlight on Corbyn’s fence-sitting, the wobblier Labour look.

But Johnson has a tricky job selling his plan while also trying to insulate it from scrutiny. He wants people to know there is a deal, but not to care what is in it. There is a flaw in the strategy that makes Brexit the central issue, while running on a platform that appeals to public weariness with the topic. That problem feeds back into the incumbency issue. There is something dissonant in a campaign that says vote for me so we can end this nightmare that I told you would be brilliant; vote for the Tories to move on from the only thing Tories seem to care about. Hardline Conservative Eurosceptics have so much pent-up revolutionary frustration, they think they haven’t even started yet. That blinds them to the possibility that the public are tired of having them around.

A six-week campaign is long enough for those contradictions to show, especially with Nigel Farage flapping around drawing attention to them. His claim that Johnson’s deal does not effect a clean enough break is ridiculous – it is a severe separation – but the Brexit party had nowhere to go but harder still. And its target audience has been groomed by Tory radicals to feel betrayed by anything that postpones the gratifying instant of rupture. Already Johnson is being tested on post-Brexit transitional arrangements. He says they won’t have to be extended beyond December 2020.

Facebook Twitter Pinterest A Brexit party supporter in Derbyshire on Tuesday. Photograph: Christopher Thomond/The Guardian

They will. A free-trade agreement with Brussels cannot be negotiated by the end of next year. The going rate is more like five years. Under Johnson’s plan, a miserably familiar landscape sweeps into view: Brexiteers pretending something impossible is easy, ruling out compromise and denouncing as traitors any who counsel delay. Meet the new rows over Europe, same as the old ones.

The Liberal Democrats have correctly identified article 50 revocation as the efficient way to settle the technical question of Britain’s future relationship with the EU, but it is not something any government likely to be formed after this election could reasonably do, as Jo Swinson must know. The politics of aborting Brexit are as gruesome as the economics of going through with it. There is no good outcome now, only different routes to realising that it was a stupid idea in the first place.

With a sustained display of incompetence, cowardice, delusion and ideological mania, British politics has created a situation so monstrous and writhing with venom that the public cannot bear to look at it. Brexit is like the mythical Gorgon that turns to stone all who meet its gaze. It must instead be stalked indirectly, using the monster’s reflection in their polished shield.

That is why the election will be only obliquely about Brexit. It will not feature rational evaluation of Britain’s relationship with the rest of Europe. These campaigns never do. The referendum drove big red and blue buses down every social fault line in the country without arriving at a functional definition of Brexit. The 2017 election was more animated by fox-hunting and dementia care than customs unions and regulatory alignment. Even when politics appears to be about Brexit, it conspires to be about something else: jostling for position in a Tory leadership race; pro-remain guerrilla manoeuvres in the remote hills of Commons procedure.

With parliament dissolved, anything relating to the substance of negotiation in Brussels will fall off the agenda because it is a boring subject for most voters and always has been. Meanwhile, neither of the two candidates to be prime minister is going to offer an honest appraisal of why leaving has been so difficult and why it brings no material benefit to the country.

Elections used to bring us solutions. The 2019 general election won’t | John Harris Read more

There will be ample talk of something called Brexit, but that word will continue to be a proxy for grievances only tangentially connected to EU membership. Or it will be a tint on the lens through which other issues – the NHS, crime, education – will be projected. If British politics was capable of sustaining a focus on the banal reality of continental integration it would have happened by now. And of all the climates in which to cultivate measured debate on the subject, a frenzied, polarised election campaign is the least hospitable. We will get to the end of it and, whatever the result, the monstrous tangle of ugly Brexit choices will still be there. The Gorgon will not be slain.

• Rafael Behr is a Guardian columnist