MPs on Thursday will face a clear choice: pass Theresa May's Brexit deal by next Wednesday or face a lengthy extension of the article 50 deadline.
Downing Street sources on Wednesday night declined to speculate on the length of such a delay to Brexit but officials in Brussels suggest that a long extension could last for anything from nine to 21 months.
The deal has been rejected twice, by 230 votes in January and by 149 on Tuesday. Attorney general Geoffrey Cox’s lukewarm legal advice made it impossible for the DUP to support the deal and offered an inadequate ladder for anxious Brexiteers to climb down.
The DUP remain the key to the success of a third meaningful vote (already dubbed MV3 at Westminster) early next week. But the prime minister knows that no further concessions, clarifications or assurances are available from Brussels.
She does have a chance of persuading the 10 DUP MPs to change their minds, however, through actions taken in London.
The first concerns the attorney general's advice, which Brexit secretary Stephen Barclay suggested to Jacob Rees-Mogg in the House of Commons on Tuesday night could be changed – or clarified.
Earlier in the day, Mr Cox had skated lightly over article 62 of the Vienna convention on the law of treaties, which allows one party to unilaterally exit a treaty if there has been “a fundamental change of circumstance”.
Mr Barclay said that if Britain believed the objectives of the Northern Ireland protocol were no longer being proportionately served by its provisions because it was no longer protecting the Belfast Agreement in all its dimensions, it could seek to walk away from it.
“Article 62 of the Vienna convention on the law of treaties, which is reflective of the customary international law, permits the termination of a treaty in such circumstances.
"It would, in the Government's view, be clear in those exceptional circumstances that international law provides the United Kingdom with a right to terminate the withdrawal agreement," Mr Barclay said.
His answer was not enough to persuade Mr Rees-Mogg or the DUP to back the Brexit deal but with a little more work from Mr Cox, it could become more persuasive.
The government could also introduce domestic legislation to give Stormont something like a veto over dynamic harmonisation of regulations under the backstop, although this could create problems with the EU.
Such measures, alongside the threat of tariff-free access to the North for Irish goods and the fear that a long delay could stop Brexit altogether, just might be enough to offer a chance of victory for the prime minister on the third attempt.