Following up on this post, what are we to make of today’s news? The UK put forward a proposal to maintain “regulatory alignment”, which is apparently not the same thing as a lack of divergence, “on the island of Ireland”. In the terms of the previous post, this means either option b) – a sea border – or option c) – no border. The whole of the UK maintaining the alignment would, by definition, maintain it on the island of Ireland. So would giving Northern Ireland a special status and creating a sea border.

If it is option b), though, this is intolerable to the DUP, a party that exists to provide absolute certainty that it will veto anything that divides NI from the UK. And that’s exactly what the DUP did, via a 20 minute phone call to the prime minister. So why bother make an offer you know will be rejected? The DUP’s statement last week made it very clear they would veto any hint of a sea border, while saying precisely nothing about a UK-wide arrangement.

The answer may be a question of sequencing. Consider this tweet from BBC political editor Laura Kuenssberg, earlier on when the deal was still a thing:

2. If you're not into Brexit politics this is going to sound completely mad but… May might agree today that N Ireland can basically be like Norway (high alignment model) before the cabinet has decided if the rest of the country is going to be Norway or Canada (low alignment)

— Laura Kuenssberg (@bbclaurak) December 4, 2017

Indeed. The proposed deal would commit part of the UK to a Norway-like status, leaving the rest of the country’s status open. But any different status for the rest of the UK would now trigger the DUP veto. This sounds a lot like an effort to deal with the multiple veto actors separately. There are quite a few – fortunately, the EU Commission and the Republic (and indeed the nationalist community in NI) are so closely aligned we can think of them as one unit. Then there are the DUP, the hard-Brexit caucus within the Tories, and the anti-Brexit majority in the Commons.

May’s original concession was worded to sound specific to Ireland, and squared veto actor no.1. Had it gone ahead, the next challenge would have been veto actor no.3 – the hard-Brexit caucus within the Tories. After all, veto actor no.1 has been promised either a sea border or no border, and veto actor no.2 will veto a sea border. The only option that is still not vetoed is no border. In this scenario, the boot is on the other foot. The DUP’s veto is now working for the prime minister, as it constitutes a self-binding commitment that constrains her from making concessions to the hard-Brexit MPs. (I see Robert Peston also noticed this.)

In the ultimate test, pushing too hard might cause the DUP to implement its veto by ending its support for the government, and either cause a general election the Conservatives would probably lose or else drive the prime minister back on the support of the anti-Brexit majority of the Commons.

It’s not a bad plan. The problem, though, is that it requires keeping the DUP sweet between the first and the third step in the sequence. A conjurer would see this as a trick with a set-up and a reveal, that needs some prestige or stage business to fill the gap between the two. Getting back to negotiating theory, though, between making the concession to veto actor 1, and confronting veto actor 3, there is a period when veto actor 2 needs reassurance – a costly signal or a side-payment – that the confrontation will actually happen. Also, the hard-Brexit caucus would have every interest in trying to sway them, as beyond this point their position is quite weak.