It may seem unimportant to those unconcerned with the Union, but it is crucial to Unionists. It would be a hole below the waterline for the Union, if allowed to stand.
The DUP, at least several of the leadership, might have been willing to adopt the UUP position on it, running the Assembly and hoping Boris would rescue them. But they knew that would finish the DUP.
A lot could be said about the DUP's messing that led to the Protocol, but the ordinary Unionist has given them the chance to redeem themselves on it. If they weaken, they will not be forgiven.
I can see how Nationalists might think the real reason is a refusal to play second fiddle to SF now that SF is due 1st Minister. And the refusal of all Unionist parties to affirm they would accept a Deputy role supports that. But only the Agreement rejectionists think like that - TUV, with maybe a few DUP old guard.
The Unionist parties should have had the honesty to affirm their willingness to take the Deputy role, if SF had the largest number of seats. They would always have done so, however reluctantly.
The only proviso is that the Agreement was working properly. It has been, albeit with hiccups like the RHI scandal. But the Protocol ended that. It is a direct tampering with the Union, without Unionist consent. If it stands, the Assembly will fall. This is not a Unionist ploy.
Who knows where this could end? Boris could refuse to budge and threaten Direct Rule with a strong Irish dimension. Even Joint Authority. It won't change hearts. Much better to remove the constitutional problem and get back to working together, even if it is with a SF First Minister.
⏭Ian Major grew up a heathen Protestant, was converted at 17. He lives out his Evangelical faith as a Baptist.