Key supporters of Mr David Trimble are predicting an overwhelming majority in favour of the devolution/decommissioning deal at Saturday's historic meeting of the Ulster Unionist Council in Belfast.
Despite the controversy generated by remarks in the US attributed to two leading republican figures, Mr Pat Doherty and Mr Martin Ferris, and Mr Trimble's insistence that the Sinn Fein leader clarify the party's position on decommissioning, UUP sources last night confirmed that the council meeting will proceed as planned.
Mr Doherty has expressed "dismay and deep concern" at the reporting of his remarks to the editorial board of the Boston Herald. He said any suggestion that he "deviated in any way from the Sinn Fein position spelt out this week in statements in Belfast is entirely wrong".
While Mr Trimble's opponents insist Saturday's vote will be a close-run thing, Mr Ken Maginnis MP said: "I'm genuinely astonished at the level of support among members of the public for David Trimble's position. It is much more enthusiastic than I would have expected, and I think that will be reflected by those who have to make the decision on Saturday."
It is also understood Mr Trimble has not given up hope that Mr John Taylor might yet stage a final about-turn and back the deal. The UUP leader, however, is leaving nothing to chance. He will fly straight back to Belfast for a round of meetings with key constituency officers this evening after today's Commons statement by Mr Peter Mandelson.
The Irish Times has learned that Mr Mandelson's intervention with the UUP leader saved the Mitchell review.
With Senator George Mitchell just "minutes away" from a statement concluding his review in failure, The Irish Times has established it was Mr Mandelson who persuaded Mr Trimble to put the devolution/de-commissioning deal to the UUC despite the original opposition of seven Assembly members.
Authoritative sources said Mr Mandelson's role had been "absolutely crucial" at a point when Mr Trimble thought he lacked the "quality" of majority necessary to take the deal to his rank and file.
Mr Mandelson will report to MPs on developments and confirm arrangements for the passage of legislation to transfer power to the Assembly following the intended appointment of the power-sharing executive next Monday.
He is expected to give Mr Trimble what one source described as "a wide degree of comfort" when addressing the so-called "fail-safe mechanism", the review clause which would see the executive fall should IRA decommissioning fail to materialise.
It is expected that Mr Mandelson will spell out the British government's expectation - shared with Dublin and Washington - that the devolution and decommissioning elements of the package "will stand or fall together".
Contrary to one report at the weekend, Mr Mandelson is not expected to set any date for the start of decommissioning.