The hardening of Boris Johnson's language on the backstop, ruling out a time limit or a unilateral exit clause, marks a dramatic turn that makes a no-deal Brexit more likely. Throughout the Conservative leadership campaign, Johnson has chosen his words about Brexit carefully, often sticking to a formula about how he would negotiate a better deal.
In his interview with Andrew Neil last Friday, he allowed himself some wriggle room on the October 31st deadline, saying it would be a mistake to signal "now" that the date could be changed. Optimists believed that in office Johnson could move towards a demand on the backstop that the EU would regard as negotiable.
The EU was always likely to hold rigidly throughout August and September to its position that the withdrawal agreement could not be renegotiated. But if Britain came in October with a demand for a time limit or an exit clause to the backstop, Ireland would come under pressure to move towards a compromise.
By rejecting these changes as inadequate and insisting that the backstop must be ripped out in its entirety, Johnson appears to be setting a course for a no-deal Brexit. Parliament will seek to block such a move, perhaps by obliging the new prime minister to return to Brussels to seek an extension to the October 31st deadline.
Johnson has promised to hold to that deadline “do or die” but he has also said he would not break the law to pursue Brexit, so he could seek a six-month extension in order to hold a general election. Calling an election before Brexit is delivered would break another of his campaign promises and risks Nigel Farage’s Brexit Party surviving as a threat to the Conservatives.
But perhaps Johnson’s language on the backstop means something else. He has characterised it as an instrument the British government designed for its own incarceration in the single market and the customs union.
Another version has always been available, the Northern Ireland-only "skinny backstop" which would leave the rest of the United Kingdom free to leave the EU's regulatory sphere. After a recent meeting with Arlene Foster, Johnson said he would not accept any deal "that sees Northern Ireland out of the UK's customs territory". He did not mention regulatory alignment.