Weekend talks with the Rev Martin Smyth could prove crucial in determining Mr Jeffrey Donaldson's immediate political future and the scale of his proposals for a unionist realignment.
This became clear last night amid signs that dissident Ulster Unionists may be planning a fresh challenge to the authority of the party leader, Mr David Trimble, next week.
Speculation about Mr Donaldson's plans soared again with confirmation that leading anti-Belfast Agreement figures are to hold a press conference in Belfast on Monday. However, the significance of this, and indeed whether it goes ahead, would seem to turn on Mr Donaldson's discussions with the Mr Smyth, the South Belfast MP who is also, importantly, the president of the UUP's ruling Ulster Unionist Council.
Sources confirmed last night that it is Mr Smyth - and not, as is widely supposed, the former party leader Lord Molyneaux - who is the critically important figure at the centre of Mr Donaldson's consultation with colleagues over his threat to quit the party following his narrow defeat by Mr Trimble at last Monday's meeting of the council.
Mr Smyth scooped just over 43 per cent of the vote in his own leadership challenge to Mr Trimble, launched at just two days' notice, in March 2000. As president of the party, and a former Grand Master of the Orange Order, Mr Smyth wields considerable influence with the party's rank-and-file members. Were he to join Mr Donaldson in a resignation pact, party sources agree it could persuade others such as Lord Molyneaux and South Antrim MP Mr David Burnside to think again and follow suit, so increasing the possibility of a mass exodus from the UUP. Senior figures in Dr Paisley's Democratic Unionist Party acknowledge that this would greatly increase Mr Donaldson's influence in shaping a formal realignment of unionist forces in preparation for an Assembly election.
The same DUP sources say they believe Mr Donaldson's final decision will be governed by principle "rather than by any calculation about what's in it for him" and that they do expect him to make good his resignation threat.
However, while it is believed Mr Smyth does not rule out the possibility of an eventual split from the UUP, the indications are that he and Mr Donaldson's other anti-agreement colleagues still regard the attempt to change the party's direction as "unfinished business". It appears they are also being influenced by renewed reports that a small number of pro-agreement Assembly members are again questioning the viability of Mr Trimble's leadership.