In Northern Ireland, an ill-tempered election campaign ends today, as voters go to the polls to elect MLAs (Members of the Legislative Assembly) to the Stormont Assembly. The province’s power-sharing executive collapsed in February, when the DUP first minister, Paul Givan, resigned in protest at the Northern Ireland Protocol.

Although the opinion polls are inconclusive, there is a real possibility that, this time, Sinn Fein will be the biggest party at Stormont. That would give it the right to nominate Northern Ireland’s first minister, when the parties try to revive the devolved government.

The first minister’s role carries identical powers and responsibilities to the “co-equal” deputy first minister, but the symbolism of an Irish nationalist holding the nominal top job would undoubtedly be a blow to unionist morale.

The party can rely on its viciously anti-British supporters

With that in mind, the campaign has featured two prominent themes.

Firstly, unionist parties have emphasised the importance of dealing with the protocol, which created a trade border between Great Britain and Northern Ireland, while nationalists and pro-EU “others”, like the Alliance Party, claim that voters are unconcerned about this issue. In 2024, the Assembly will vote on whether to extend critical aspects of the sea border.

Secondly, the DUP has argued that if voters do not make it the biggest party, republicans will win the election and deliver a “border poll” that threatens to remove Northern Ireland from the UK. Sinn Fein, meanwhile, has become unusually coy about discussing its aspirations for an independent, all-Ireland republic.

Instead, the party has spent a lot of time talking about the “cost of living crisis” and claiming it will find extra funding for the health service. After a survey showed that less than a third of people would vote for a “united Ireland”, if it were offered tomorrow, Sinn Fein’s “northern leader” Michelle O’Neill admitted, “I don’t think people woke up this morning thinking about that.”

In the Irish republic, the party presents itself as a left-wing alternative to the political establishment. In Northern Ireland, Sinn Fein has tried a similar trick this time, using the slogan “vote for real change” even though it has formed an important part of the power-sharing government since 2007. This message may lack credibility, but the party can rely upon the atavistic impulses of its viciously anti-British supporters.

The prospect of a Sinn Fein first minister will appal and alarm many voters. The party celebrates its terrorist past openly and security sources believe it still takes direction from the IRA’s army council.

At the same time, in Northern Ireland’s political system, the identity of the first minister is largely symbolic. If the post is held by a nationalist, then a unionist will occupy the co-equal deputy’s role, and vice versa. In any case, the DUP remains adamant that, unless the protocol is reformed, it will not participate in power-sharing, so the most likely outcome remains that there will be no executive at all for the foreseeable future.

Sinn Fein’s support has fallen since the 2017 Stormont election

Unless the government can quickly sort out the sea border and do it properly, either through legislation or negotiations with the EU, then the poll will probably be followed by yet another political crisis.

For many people, the main issue in this election is not whether Sinn Fein can edge out the DUP to become the biggest party. It’s whether the overall unionist vote can be maintained, or even increased, so that voters send an indisputable message that the sea border, in its current form, is unacceptable.

Although Sinn Fein is ahead in most opinion polls, significantly its support has actually fallen since the 2017 Stormont election. It is in the lead only because the DUP has shed voters at an alarming rate, mainly to unionist rivals. At the same time, polling struggles to reflect the complexities of Northern Ireland’s proportional, Single Transferable Vote electoral system. Voters rank candidates in order of preference and the supporters of rival parties have traditionally been reluctant to include Sinn Fein among their “preferences”, which can be decisive as the counts progress.

Some of the eight per cent dip in the DUP’s support may be down to a revived, moderate Ulster Unionist Party (UUP). But most of those voters seem to have moved to the harder-line Traditional Unionist Voice (TUV), which is less compromising on the protocol and heavily criticised the DUP’s response to the sea border.

If the three main unionist parties, and pro-Union independents, record a strong collective vote, then any Sinn Fein victory will be hollow. The party probably will press for a border poll regardless, but if nationalist support is significantly behind pro-UK sentiment, then its arguments will remain ineffective.

On the other hand, if unionist voters turn out in poor numbers overall, it may not mean that a constitutional referendum is likely, but the protocol that undermined Northern Ireland’s place in the UK could become harder to dislodge.