The challenge for the DUP now is the work of rebooting unionism and appealing to a wider section of NI society
For many unionists today, the mood is a desultory one. How has it come to this?
Not for the first time do they find themselves staring at a Conservative Prime Minster and shouting accusations of 'betrayal' and 'traitor'.
How fortunes change. For the past couple of years the DUP have been at the heart of Government thanks to a confidence-and-supply deal which brought £1bn of new Government money to Northern Ireland.
There were city deals, high-profile guests at party conferences and a general sense of being only one step away from a seat at the Cabinet table. Now, that close relationship would appear to lie in tatters.
Let's be clear - parliamentary votes are always for sale and their currency fluctuates with the fates of the Chamber. Political honeymoons always come to an end. This will not be lost on Arlene Foster or her deputy Nigel Dodds.
Ironically, the party is being criticised for putting the Union first, something her critics should have divined from the name of her party. The other unionist parties are standing united with them in this view.
However, Lord Trimble's intervention yesterday that he backs the deal is thought-provoking. No one could doubt his unionist credentials and he has been a forceful critic of previous proposed agreements. He said the deal brokered between the EU and the UK was within the spirit of the 1998 Good Friday Agreement. "Whilst, previously, the people of Northern Ireland were to have an agreement imposed on them, now we have a mechanism for the consent of the people of Northern Ireland," he said.
Please log in or register with belfasttelegraph.co.uk for free access to this article.
Just as it's a numbers game at Westminster, unionism is also staring at a numbers game closer to home when it comes to consent.
There is an argument that if there were to be a poll on the border the key demographic would not be republicans but nationalists - those who are there to be persuaded that the Union offers a better future for them and their families in the new Northern Ireland.
The challenge for the DUP is to find a modern 21st-century iteration of unionism that can appeal to a wider section of society.
And then they need to find a way to sell that.
Arguably a party that could sell power-sharing with Sinn Fein to its support base could sell anything.
While undoubtedly the mood of the DUP at Westminster today is likely to be sombre and angry, an early general election could rearrange the tectonic plates of British politics yet again and who will be the winner.
And today doesn't mark the end of Brexit but rather the beginning of another long process. The work of rebooting unionism needs to start straight away.