The key players need a Brexit deal. At this stage, there’s only one option

Dublin, the DUP and Boris all have to compromise in pursuit of agreement or risk political disaster

With a European summit looming, the Brexit negotiators of all sides are agreed on only one thing – there are just a few days left to do a deal. And in these few days there are three key decision makers who will effectively determine the outcome.

One, of course, is Boris Johnson himself. The second is Arlene Foster, leader of the DUP, whose support is needed to pass a deal through Parliament. The third is the Irish Taoiseach, Leo Varadkar. However much attention is paid to the pronouncements of other governments around Europe, they are not going to force Ireland into a compromise it doesn’t want, nor resist a deal with which it is happy. So on the EU side, the fate of a deal will be decided in Dublin.

These three leaders are not currently on course to make a deal, although they all need one more desperately than they would like to admit. For Boris, not reaching agreement this week means fighting an election advocating a no-deal Brexit or perhaps, by some slim chance or crafty manoeuvre in the final days of October, having accomplished it. Neither is attractive for anyone wanting to be confident of winning a Conservative majority.

Much attention has been paid by Downing Street strategists to retaining the support of Brexiteers and winning over those who might vote for Nigel Farage. But it is easy to underestimate the difficulty of winning a general election without the other end of the Conservatives’ normally broad church. A hardline election message, shorn of any hope of compromise, will leave many traditional but moderate Tories with their pencils hovering over the Liberal Democrat box on polling day, and many Conservative MPS in the South West accordingly in danger of losing their seats.

Seats held in London in the 2017 election would also be in danger, as would many that were gained in Scotland. A few could be lost to sitting MPS standing as independents, whom the party has been foolish enough to expel. All of these would have to be replaced by gains from Labour in the Midlands and North. The voters there are certainly pro-leave overall, but might easily decide that Brexit is not as important to them as other issues. However you cut it, a no-deal platform makes an election a toss-up, whereas an election after both doing a deal and delivering Brexit would give Boris a crushing advantage over all his opponents.

The DUP’S need for a deal is even more pressing. It is on the verge of achieving the most rapid destruction of its own core objective in the history of political parties, anywhere in the world. That objective is to keep Northern Ireland within the United Kingdom. In three short years, by advocating leaving the EU without regard to the local consequences and then obstructing every effort to resolve the difficulties inevitably caused, it has produced an apparent surge in support for a united Ireland. A no-deal outcome would bring forward dramatically the day when Sinn Fein beats them in an election and a ‘‘border poll’’ takes place.

Perhaps recognising this danger, the DUP has now agreed that Northern Ireland could stay within the orbit of EU regulations after Brexit, but only subject to the renewed consent of the Stormont assembly every four years. Since it could then vote to leave that arrangement anyway, if the assembly could ever agree to meet, it is not surprising that this does not go down well on the other side. It would be in its own interests to make a further concession – that any future departure from single market rules would require, just like the formation of an executive in Belfast, the agreement of both nationalist and loyalist communities.

If Mrs Foster could bring herself to make that crucial move, then the third decision maker, Leo Varadkar and the Irish Cabinet, would face a much more finely balanced judgment. They too will face very serious problems in the event of a no-deal Brexit. While the economic consequences of an unprecedented event are difficult to forecast, it seems reasonable to assume that they would be roughly as serious for Ireland as for the UK.

Even more important for them, no deal brings for Dublin the very outcome it has striven to avoid all along – the imposition of customs checks on the island of Ireland. It might choose to gamble that refusing a deal will result in a change of government and a reversal of the 2016 outcome in a new referendum, but that is a very risky bet. It would be in its interests, if the ‘‘consent’’ issue were resolved in its favour, to summon the political will to work with London on how to make a customs arrangement work. Difficult as it is, its predecessor, before the current Irish government came to power, gave every indication it would find a way of doing that.

There is, therefore, a rational agreement to be made, and powerful reasons for all three principal participants to make it. Yet the chances of it happening are low. That is partly because these are such complex matters, and the time available is very short. But it is also because so much time has elapsed since the referendum: Irish leaders have spent so long saying that any customs checks are incompatible with the Good Friday Agreement that they have persuaded themselves of it; the DUP has got so used to digging in, it has lost the ability to dig itself out.

In negotiations bogged down and blocked by complexity, it is sometimes a simple solution that leads to the breakthrough. There is just one of those available – to take Theresa May’s deal but add a time limit on the Irish backstop. That would involve a major climbdown by all three players, but could be implemented with a single sentence.

Had such a provision been made before, the deal would have passed the Commons in March. Ireland would lose less by this concession than it thinks, as it will never hold a sovereign country to an agreement indefinitely against its will.

It will be worth trying such an idea or an equivalent one at the last minute. Otherwise all three of these pivotal leaders will look back on this week and realise they needed a deal more than they ever knew.