This morning’s papers report that Sir Jeffrey Donaldson, the leader of the Democratic Unionist Party, has reiterated his threat to collapse devolution in Northern Ireland. The MP urged Liz Truss, who has taken over negotiations on the Protocol, to set a firm deadline for triggering Article 16 if she hasn’t made sufficient progress.

According to the Sunday Telegraph, Whitehall views this intervention ‘unhelpful’; they have apparently been trying to avoid hard deadlines in order to give negotiators the space to work.

But one can understand why Donaldson might wish to force matters. As I noted when Lord Frost resigned, recent months have seen a noticeable softening of London’s negotiating position. Serious talk of triggering Article 16 in November came to nothing, and it isn’t yet entirely clear why. Dominic Cummings has suggested that there is simply insufficient Prime Ministerial will to see such aggressive tactics through (but then, he would).

Donaldson isn’t the only one keen to make progress – or at least, make the issue go away. Last week the Irish Government warned that the upcoming Stormont elections should not become a ‘referendum’ on the Protocol. Apparently London and Dublin are also treating February as an “informal cut-off point” for negotiations.

It remains an open question whether the DUP will actually collapse Stormont. They are an Assembly-based party; it furnishes them with jobs, titles, salaries and status. Coherent, ‘Carsonite’ integrationist unionism is not their game, and there are plenty of commentators who are deeply sceptical that there is any truth to Donaldson’s posturing against the institutions.

Moreover, there would be a big difference between this collapse and those precipitated by Sinn Fein, who hold the institutions to ransom only for things that Westminster can provide unilaterally, such as more powers or cash. Permanent changes to the Protocol are not in the Secretary of State’s gift; the DUP would therefore risk ending up with a choice of admitting a high-profile defeat to go back in without concessions or seeing Stormont shuttered for much longer than they might like.

One factor which does perhaps make it more likely than previously is that Donaldson is an MP, rather than an MLA. He would therefore not lose his platform in the event that Stormont fell over yet again, and the shift in focus towards Westminster (where Sinn Fein don’t sit) might do him some favours.

But even if he doesn’t follow through on his threats, absent some real changes Donaldson isn’t going to drop the subject for the elections. Hostility to the Protocol is one thing that unites most of the current Unionist vote (even if it is less important to the wider potential unionist vote).

And the DUP need such a unifying theme. To their right, the Traditional Unionist Voice will pounce on any softening of position, and try to do to the DUP what the DUP did to the Ulster Unionists in the Noughties.

Meanwhile their left flank is threatened by Doug Beattie’s UUP. A campaign centred on a constitutional question of existential importance to unionists would seem to favour the DUP’s efforts to maintain their position as the dominant Unionist party, rather than giving Beattie the space to try to broaden the campaign out to social issues and the need for an overall refresh of pro-Union leadership. (The other factor doing this, of course, is the threat of a Sinn Fein first minister.)

A Protocol-focused campaign gives the UUP leader the choice of either taking a similarly tough stance as Donaldson, in which case the larger party will likely eclipse him if voters are merely looking for the most effective anti-Protocol vote, or taking a softer line which the DUP will hammer him for.