Tomorrow Northern Ireland and the rest of the United Kingdom will vote in the elections to the European Parliament.
It is not even clear whether the three MEPs will in fact ever take their seats. They will not do so, for example, if Theresa May passes her withdrawal agreement next month, and the UK leaves the European Union.
Almost all unionists should hope that the MEPs do take their seats, because the exit deal that she has negotiated with the EU does serious constitutional damage to the UK.
By tying Northern Ireland to EU regulations and keeping it fully within the customs union, while having a slightly different customs arrangement for Great Britain, it paves the way for a full future Irish Sea border (regulatory and customs).
It is essential therefore that the deal is defeated, and that unionists poll well tomorrow. The only three candidates who oppose the backstop, Diane Dodds, Danny Kennedy and Jim Allister, have all advised voters to transfer between them.
A lower than usual unionist turnout will merely be interpreted as general support for the backstop in NI.
A higher unionist turnout — markedly higher than was seen in the council elections – will counter any such analysis.
This is a perilous time for unionism. A chronically weak secretary of state is not competent to challenge a determined nationalist Ireland over anything: over its stance towards Brexit, over a legacy approach that helps rehabilitate IRA terrorism, or over Sinn Fein’s Stormont veto.
Theresa May will probably be gone within weeks, but her successor might be someone who tries to revive her deal.
Even Boris Johnson, who is favourite to inherit the Tory crown, in the end voted alongside Jacob Rees Mogg for the agreement of which they were previously scathing.
The results of this election, both nationally and locally, will be seized upon by the victors as a mandate for a way forward not just on Brexit, but in government as a whole.
That is why voter participation tomorrow is so important.