Cautionary tale for gullible DUP
Regardless of the outcome of today's finely balanced vote in the House of Commons, it is clear that the DUP's decision to enthusiastically support the Brexit project will go down as among the worst strategic blunders in the history of unionism.
Several senior DUP members were well aware of the risks presented by the 2016 EU referendum, and encouraged the party to either take a neutral stance or lean towards the leave side in fairly tentative terms.
Instead, leading figures were persuaded not only to play a central role in the Brexit campaign, including an involvement in some highly unusual financial dealings, but also to ultimately form a close alliance with Westminster's most Eurosceptic elements.
This led to them to a very public endorsement of Boris Johnson during his calculated and ultimately successful attempts to first undermine Theresa May as prime minister and then take her job.
Many voices warned the DUP that he was not to be trusted and would inevitably ditch the party when it had outlived its usefulness in terms of his personal ambitions.
However, the courtship of Mr Johnson escalated to a stage when he was cheered to the rafters at the DUP conference a year ago in scenes which the party's front bench must now be trying to erase from their collective memory.
Mr Johnson proceeded to sign a deal with EU earlier this week which contradicted all his previous assurances to the DUP and left the party effectively spluttering with indignation on the parliamentary sidelines.
Further twists and turns in the Brexit saga will undoubtedly follow but what will not change is the reality that it has placed the future of the border in Ireland close to the top of the European political agenda in an entirely unprecedented way.
The measured approach of the Dublin government has won the firm support of the rest of the EU 27 at a time when Mr Johnson's Machiavellian manoeuverings have exposed how far maintaining the union has been pushed down his list of priorities.
It is widely believed that the DUP initially signed up to the Brexit initiative on the assumption that the vote would be lost but valuable relationships could be established along the way.
Instead, the leave side's cynical tactics allowed it to squeeze home three years ago and then consistently exploit a gullible DUP until the bitter end on Thursday. It is a cautionary tale and it is far from over.