Suzanne Breen: Boris Johnson unequivocal but can he really be trusted?
These are dangerous times for the DUP and the party will have breathed a massive sigh of relief when the Prime Minister ruled out a Northern Ireland-only backstop.
It's one thing for Boris Johnson to reassure the party privately during his tete-a-tete with Arlene Foster in Downing Street. But for him to do so publicly inspires considerably more confidence.
The Prime Minister was unequivocal in his remarks.
"The backstop is going to be removed, I very much hope. I insist. It's the only way to get a deal," he said in a Facebook live Q&A.
"We will not accept either a Northern Ireland-only backstop, that simply doesn't work for the UK.
"We've got to come out whole and entire and solve the problems of the Northern Irish border and I'm certain that we can do that."
Yet we must remember Mr Johnson's history. Just six months ago he became the latest Englishman to betray unionists.
Please log in or register with belfasttelegraph.co.uk for free access to this article.
Despite his denunciations of Theresa May's withdrawal agreement and the controversial backstop - and his love-in with the DUP at its annual conference - he walked through the Aye lobby to support her deal.
Other unionist parties last night pointed out that the backstop is far from dead and buried.
UUP leader Robin Swann said: "The Prime Minister has ruled out a Northern Ireland-only backstop at the minute, but he will come under pressure closer to the end of October. I wouldn't rule out the chance of him moving his position."
TUV leader Jim Allister welcomed Mr Johnson's "clear commitment" that a Northern Ireland-only backstop "is out of the question".
But he stressed that the Prime Minister must be held to his pledge "both in letter and spirit".
Mr Allister said: "The backstop by another name, or a partial backstop, is equally unacceptable.
"Suggestions in recent days of an all-Ireland agri-food regime should be rejected by all unionists as such alignment will require and mean that it is the EU writ and not the UK writ which would run in Northern Ireland."
The DUP knows that if any deal doesn't sit with the party's previous commitments, its rivals will be lining up to accuse it - and not just Mr Johnson - of betrayal.