The threat that the DUP might vote against the Budget if it isn’t happy with where the Irish border backstop is after the October European Council all fits with their effort to persuade Number 10 that they really are serious. As I say in tomorrow's Spectator, some in government believe that, ultimately, May is going to have to call the DUP’s bluff on extra regulatory checks in the Irish Sea. They argue that the DUP will never risk putting Jeremy Corbyn, a man who favours a united Ireland and was deeply sympathetic to the IRA, in Downing Street.
But I understand that the DUP have privately emphasised to several Cabinet Ministers that they really would be prepared to vote down the withdrawal agreement and risk a Corbyn government if that is what was required to prevent the emergence of any new barriers between Great Britain and Northern Ireland.
Now, there are two big questions here. One, if the whole of the UK, supposedly temporarily, stays in a customs union with the EU, can the checks that the EU wants be so reduced as to become acceptable to the DUP? I understand that the DUP’s message to May is that they’ll accept an intensification of existing checks, but no new checks. Second, are the DUP prepared to follow through on their threats? On the one hand, they are dug in and this is becoming an existential issue for them. On the other, they have a uniquely powerful position in this hung parliament and would likely lose that if the government fell.
What’s for certain is that no one can be certain how this will all unfold. It is time to hold on to your hats.