There is enough uncertainty over the next year to give him a decent chance

When Ian Paisley said “No!”, people believed that he meant what he said. The Big Man may be gone but his party lives on and it would be extremely unwise for anyone to assume that when Arlene Foster says “no”, she means any different from her predecessor. The DUP do not bluff. Ever. They might occasionally change their minds but when they do, they do so in their own time and on their own terms.

All that ought to be obvious to anyone who has paid any attention to N Ireland politics, which presumably rules out the N Ireland secretary. Which is why it was a measure (and perhaps an explanation) of the difficulties the government is in to see a tweet from the political editor at UTV stating that many senior Tories at Westminster believe that the DUP is bluffing when they threaten to veto the Budget and, implicitly, bring down the government in the Confidence vote that would inevitably follow.

Presumably, the government’s thinking is twofold. Firstly, that the DUP have the balance of power and, hence, huge leverage. To bring down the government and precipitate an election would very likely throw away that position. And secondly, to call an election, particularly at a moment when the Tories were in turmoil, would be to invite IRA-sympathising and United Ireland supporting Jeremy Corbyn into Number Ten: not exactly an appealing prospect for hardline unionists.

But to think along those lines is to misunderstand the situation. Governments come and governments go. At some point, the Conservatives will lose power and in all probability, Labour will replace them. That might be this year, it might not be until the 2030s, but at some point it will happen – and the DUP know that. By contrast, the implementation of a border in the Irish Sea would be a genuine game-changer and fundamentally alter the relationship between Britain and N Ireland (and, implicitly, between the Republic and N Ireland). If it comes to a choice between a temporary setback and a permanent one, it’s not difficult to see which the more attractive is.

Which brings us to the betting markets. For a long time, I’ve not seen any value in Jeremy Corbyn as next PM. I’ve always been of the opinion that if it looked likely that Labour would win the next election, the Tories would switch leader meaning that the next PM would come from Theresa May’s party. That thinking was based on the assumption that the Conservative administration would last through to 2022 with DUP support, which with sensible management, it should.

The Ken Reid tweet however has prompted me to reconsider.

I think there is a very real risk that May could put her initials to an agreement that crosses the DUP’s red lines, in the belief that they, like the ERG, will prove more hot air than substance. That would be a fatal error.

If she does, my guess is that it will come after the Budget and possibly not even this year.

The would present the DUP with an even starker choice. They will not want a deal that contemplates an Irish Sea border to even come to the Commons because of the risk that the government might gain enough Labour support (on what would, after all, be a soft Brexit), to outweigh ERG and DUP opposition. That means liaising with Labour to bring about a Vote of No Confidence before the Commons could vote on the Brexit deal. Given that Corbyn’s main aim is to bring down the government, he would probably go with that. After all, if he could force a general election – and form a government afterwards – he could request an extension to the A50 period and seek a different deal, one which would produce an even softer Brexit but, crucially for the DUP, no GB-NI differential.

As far as the bets go, we might not even need to think about a general election. How governments are formed after a No Confidence vote now that the FTPA is in place is unknown territory. We do have the guidance of pre-FTPA history, the Cabinet Manual, and the Act itself, but these are not exhaustively prescriptive.

If May’s government were to be No Confidenced, I would fully expect Corbyn to demand to be given the chance to form a government, which would not be an unreasonable request in the circumstances. Whether the Palace would accede to such a demand is the crucial unknown, not least because Labour wouldn’t be the only ball in motion (which we’ll come back to). There certainly wouldn’t be time to do full deals with the SNP, Lib Dems, DUP and others; Corbyn and McDonnell would have to wing it and hope for the best. Crucially, however, they would not have to prove that they could form a government: that would be to test in the Commons. The strongest argument would be that with May out of the game, the Tories couldn’t and that they might.

Importantly, as far as the FTPA goes, to head off an election, the Commons has to pass a motion “that this House has confidence in Her Majesty’s Government.” In other words, we are not talking about a potential government; we are talking about the ministers already in office. If Corbyn was to be given a chance to test support in the Commons, he would have to be PM already.

However, the Tories would be unlikely to allow that to passively happen. If May’s ministry were to be No Confidenced, there is a good – but not overwhelming chance – that she would either resign as party leader or be no confidenced, in the hope that some other Tory leader could build something from the wreckage. The problem there is that the replacement would have to be in place almost immediately. There could be no time for the election the Conservative Party constitution demands – unless there were only one candidate. If the Tories could swap leaders within days, that would place them back in the game; if not, it would leave them in a horrible position.

The enormous risk that the Tories would be taking in dumping May immediately would be that if neither Labour nor an alternative Tory could gain the confidence of the House, then a general election would be triggered before the Conservatives had had chance to complete their own election. The Party would be in a state of utter turmoil, without a leader and divided into warring factions, and having failed to deliver a Brexit Deal. The temptation would surely be for Corbyn to not try very hard to win the vote. On the other hand, if May were not ousted, there could still be a general election but in that case, with the Tories stuck with a lame duck leader whose campaigning skills have already been tested and found wanting. (And note – under this scenario, a bet on Corbyn as Next PM would be likely to still pay out).

The chance of a misunderstanding between a No 10 machine which has always been a bit tin-eared, and a DUP which sees what it stands for under existential threat, leading to the government falling means that the 6/1 available for Corbyn to be Next PM is now value.

David Herdson