If the polls are right, it's all over for Theresa May – and that's bad for Brexit

Anything less than a substantially increased Conservative majority will amount to a defeat for Theresa May. If she fails to achieve it, it is hard to see how her position will be tenable – either as leader of her party, or as head of a government set to steer the bargaining with Brussels

Now it may be that we all wake up on 9 June to learn that Theresa May’s gamble has paid off. She will have won her snap election by a landslide; she will have several dozen more Conservative MPs to swing any Commons vote, and she will have secured the best possible mandate, personal and political, to embark on negotiating the terms of Brexit.

Just maybe, though, she won’t.

Recent polls suggesting a hung parliament or even a Conservative defeat look implausible, though it would be life-enhancing to believe that this election has turned from a walkover into a proper contest. And the spread of results indicated in the polling generally – from a parliament with no overall majority to a Conservative majority in double, or even triple, digits – looks impossibly wide: someone’s calculations have to be very wrong.

Yet there does appear to be a consensus on one point: the polls have narrowed, so that the sweeping majority Theresa May had banked on – and the pre-campaign polls seemed to promise – is not as much of a foregone conclusion as it once was.

Whether this is because Jeremy Corbyn’s appeal was underestimated, or because the personalisation of the Conservatives’ campaign around May was ill-advised, or because the “dementia tax” debacle and the Manchester bombing refocused the campaign away from Brexit, or for some other as yet undefined reason, will be for the post-election analysts to judge. But it is not necessary to entertain the prospect of a hung parliament or even a Conservative defeat – let’s not push the speculation too far – to realise that anything less than a substantially increased Conservative majority will amount to a defeat for Theresa May. It will also, once again, alter the political calculus around Brexit.

Take the Prime Minister first. She called an early election, despite months of insisting that she would not do so, on the basis of exceptionally favourable opinion polls and a well-founded hope of gaining a stronger parliamentary mandate for the Brexit negotiations that was also hers. If she fails to achieve this, it is hard to see how her position will be tenable, either as leader of her party – calling the election would have to be considered as great a misjudgment as David Cameron’s decision to call the referendum – or as head of a government set to steer the bargaining with Brussels.

So far, May has declined to answer questions about how she might respond to an election result that leaves the Conservatives little better off than before, though she has said that, if re-elected, she would serve out a full five-year term. And few leaders commit to resigning before the worst has actually happened. Cameron did not, even though it was obvious that a lost referendum would give him little choice, and May will not do so either. How long she could continue in office after a poor result, however, is a valid question. There are reports of knives being sharpened already in the Conservative hierarchy.

The implications of a surprise result for Brexit and the Brexit talks are, if anything, even greater than for Theresa May. What would it mean that a prime minister who went to the country seeking an explicit parliamentary mandate for Brexit had essentially been rebuffed? (And this would surely be the significance of anything less than a clearly increased majority.)

As seen from Brussels – or Berlin or Paris – the British bargaining position would be substantially weakened. The Government’s mandate would be a lot less convincing than it would have been without a vote. How would any UK prime minister then proceed?

One consequence could be that the initiative passes from the Government to Parliament. Given that the election post-dated the referendum, a slim victory for May (or less) could encourage those many MPs with misgivings about Brexit to take another look at the “will of the people”. They could well argue that now an election had been fought on Brexit – after all, this is what Theresa May intended, even though many other issues came to cloud the vote – the “will of the people” was rather less clear.

Whether there would be a sufficient number of MPs prepared to challenge the legitimacy of Brexit, or call for a new referendum, or – as the Liberal Democrats propose – legislate for a referendum on the actual terms of Brexit, would probably depend on many other considerations. But there could well be tempestuous times in the new parliament that would throw many of the May Government’s Brexit calculations up in the air.

The nub of the problem is this: an election result along the lines predicted when it was called, a big majority for Theresa May, could indeed bolster the Government’s negotiating position in the eyes of Brussels, while helping also to confirm acceptance of Brexit at home. But a different result – including one that falls short of those initial expectations, if only by a relatively small number – would have the opposite effect. Not only could it encourage Brussels to drive a harder bargain, but it could reopen the still raw Brexit wounds in the UK.

Of course, none of this may happen. It may well be that we wake up on the morning after the night before to hear an exultant Prime Minister claim a famous victory. In which case, it is game on for Brexit and for the talks scheduled to begin less than two weeks later.

If the result is anything less than that famous victory, however, the UK will be plunged into new political uncertainty, with pretty much everything that has happened in politics over the past year called into question. There would be fury among Brexiteers, a flickering of hope among Remainers, and a rejoining of the Conservatives’ internecine Europe war.

Whether that is a prospect to be welcomed or feared, I leave to your judgement as readers – and voters.