This week’s snap elections in Northern Ireland have been very bad for capital-U Unionism. The Democratic Unionists are only one seat ahead of Sinn Fein, the Ulster Unionists slipped behind the SDLP, and Unionists lost their Assembly majority for the first time ever.

Arlene Foster’s stubborn refusal to step aside, even temporarily, whilst the ‘cash for ash’ scandal was looked into seems to have done something that ten years of Sinn Fein banging the green drum has not: motivated nationalist voters to go to the polls. It’s hard to disagree with Sam McBride’s assessment that it’s been a “disaster for unionism“, or at least for the unionist parties.

Of course, it’s possible to over-sell even such results as these. Northern Ireland’s place in the UK is guaranteed by referendum and not in any immediate peril.

Nor should even the most committed unionist neglect the upside: by falling below the 30-seat threshold needed to unilaterally veto legislation, the DUP have almost certainly paved the way for Ulster to move much closer to British norms on same-sex marriage and abortion – assuming that the parties actually manage to form another executive.

In some ways, in fact, one might argue that the result wasn’t quite seismic enough. The two big parties are still the two big parties, and it will still be up to them to form the Executive. No new, policy-focused party broke into the traditional system.

Mike Nesbitt, the Ulster Unionist leader, went out on a limb to endorse the nationalist SDLP in a bid to create an ‘alternative government’. His party was rewarded with a poor result, and he’s announced his resignation.

Taken together with the fact that the DUP share of the vote barely fell, and you can just about see how the party’s leadership might conclude that trying to swallow the UUP on “block Sinn Fein” grounds and otherwise holding steady might be viable. That would be a serious strategic mistake.

As Ben Lowry notes in the News Letter, this result does mean that unionists need to start thinking about what their response to a border poll would look like. As in Scotland, it’s clear that serious thinking needs doing about the shape of the unionist campaign.

The decline of the UUP will make it harder for the capital-U Unionist parties to keep liberal-minded pro-UK voters inside the tent. Some may stop voting in elections (so-called ‘garden centre prods‘), whilst others will continue to shift their allegiance to the Alliance Party.

In the event of a border poll, this presents a problem: the Alliance are border-neutral, and won’t make any organised effort to bring their voters out for the Union. Individual Alliance politicians may try to, but if the parties and personalities providing the backbone of the pro-UK campaign have no cut-through with liberal voters that’s an obvious handicap.

And if mobilising liberal unionists is difficult, reaching out to the unaligned, and to pro-status-quo Catholic voters, is an order of magnitude more difficult again.

It’s important not to get carried away by any particular result: any situation where nationalism can be on its last legs one year and then unionism the next is very likely one where things are being over-interpreted. Nonetheless it’s clear that the DUP in particular, as the pre-eminent unionist party for the foreseeable future, needs a root-and-branch rethink.

One upside of the result is that once Northern Ireland has fallen into line with mainland attitudes on gay marriage and abortion, a major barrier to deepening relations with the Conservatives will be lifted.

This matters because anxiety about the impact of Brexit on the border, which our editor has written about, was doubtless one of the factors driving Sinn Fein support. It’s now more important than ever that the DUP make leaving the EU work for Ulster. Close collaboration with the Government will be essential.

Rebuilding that historic connection may also yield other benefits: a more liberal, outward-looking unionism, married to an actual economic policy programme, may start to win a hearing from voters who just aren’t interested in traditional DUP fare, and with foreign policy rocketing up the agenda the ability to influence the British Government directly on reserved issues may become more appealing to voters.

That’s only the shape of one possible solution, and there may well be others. But having fumbled a very strong unionist position into a calamitous electoral setback for the sake of little more than stubborn pride, the DUP owe unionism a solution.