One OF David Trimble's biographers has chosen a working title for his eagerly awaited tome: Himself Alone. Nothing could better encapsulate the manner of Mr Trimble's entry into the all-party negotiations in the autumn of 1997; his single-minded conduct of them; and the judgment call he made on that historic Good Friday seven months on, when Jeffrey Donaldson jumped ship and his party gasped in disbelief.
Nor could any two words better describe his situation this morning, just 48 hours before he will be obliged to make an even more momentous call.
Many people, nationalists included, feel immense sympathy for the UUP leader's predicament. And, in the general rush to criticise and condemn, it is fair, surely, to ask who would wish to occupy his place at this critical moment in Irish history. Plainly torn between the expectations of his powerful Prime Minister and the demands of his party, Mr Trimble sits alone at Westminster contemplating the nuclear options presented - fearing himself damned (and politically dead) if he does, and guaranteed much the same fate if he does not.
The wisdom in London and Dublin is that he would clearly like to oblige. At the crudest level, the calculation is that he certainly will be damned if he refuses to take this "final risk for peace", whereas he just might win handsomely if he gambles.
The more benign view of some key players is that Mr Trimble has actually "internalised the logic of the peace process" but is the prisoner of his party and the arithmetic of unionism's divided state.
The UUP leader has always resisted this suggestion, and denies having reached a settled view about the bona fides of the republican leadership, either before or since signing the Good Friday accord.
But, whatever about that, there is little doubt that he wants the agreement to work. Sinn Fein leaders have consistently questioned this, suggesting Mr Trimble's "engagement" never really moved beyond the tactical and strategic. However, that view is rejected by those closest to the Taoiseach, and is barely sustained by the evidence.
For the past 12 months David Trimble has had to endure the open contempt of a majority of his parliamentary colleagues, and the ever-present threat that they would depose him as their leader at Westminster. Whatever spin his aides called into play, he has watched his party record two all-time-lows in the Assembly and European elections. He knows that if the events of this week result in his removal as First Minister-designate (and there are a number of ways in which this could happen) he no longer has the absolute majority of the unionist bloc necessary to guarantee re-election at some future point.
Moreover, he sees all too plainly that if the Assembly is convened on Thursday without a prior agreement with him on triggering d'Hondt, a majority of unionists will almost certainly vote for the DUP-sponsored motion seeking Sinn Fein's exclusion.
No matter that that vote will have no effect, given the Assembly's cross-community requirements. In the vital battle for the soul of unionism, David Trimble will have been reduced to a minority shareholder.
In one best-case scenario, the Trimbleistas calculate that 38 out of 58 unionists will vote for exclusion. That presupposes nine UUP defections - four more than are necessary to give the anti-agreement forces the 60 per cent blocking share of the unionist representation at Stormont.
Although it seems far-fetched and scarcely relevant at this moment, one leading politician observed last night that it might also give Mr Peter Robinson the chance of becoming First Minister-designate should the Assembly miraculously survive the fall of Mr Trimble.
Republicans are dismissive of anything smacking of a "poor David" plea, content to blast his failure to "face down the rejectionists". And there is no doubt he has not always helped his own cause. Many, even on his own side, lament the failure to sell the agreement in terms of his reasons for signing-up in the first place. The PUP is not alone in thinking the issue on which to test republicans should always have been consent rather than decommissioning (although it must be said that no one did more than Mr Ahern to entrench Mr Trimble in the decommissioning ditch).
In any event, the objective fact is that Mr Trimble is now in a perilous position. Moreover, this moment of crisis was not of his choosing but of Mr Blair's. It was the Prime Minister who unilaterally imposed the June 30th "absolute deadline". It is Mr Blair who insists on make-or-break choices in this of all weeks. And it is he - as if the peace process is actually in his gift - who seems to threaten the end of politics if things are not done according to plan come Thursday.
Mr Trimble would still like a "soft landing" and adjournment. But even if Mr Blair was willing, it seems clear the South and the SDLP are not so minded.
If put to it, then, which of the nuclear options will Mr Trimble choose? And is there, to use a favourite Blairite phrase, a Third Way? The only one to surface thus far (advanced, it must be noted, by some of Mr Trimble's non-party friends) is that he agree to trigger d'Hondt "under protest", while placing a post-dated letter of resignation as First Minister with the presiding officer, Lord Alderdice.
The argument advanced is that Mr Trimble would thus take control, rather than be cast either as "Blair's poodle" or the prisoner of his own backwoodsmen; tie the Prime Minister to the timetable for decommissioning he spelt out in the Commons last week; spurn Mr Blair's "failsafe" in favour of his own; and, perhaps, pre-empt an early leadership challenge by assuring his party that the executive would be collapsed by his action if decommissioning has not started by a set date.
To its authors and supporters the obvious attraction is that Mr Trimble, under protest, gives Mr Blair the chance to test the "seismic" shift in republican thinking, while retaining President Clinton's option - the right to walk away. Mr Trimble, however, does not seem inclined to go down this path, and Jeffrey Donaldson has already moved to foreclose the option.
An alternative notion which has been gathering ground in internal UUP discussions, believed to have originated with Mr John Taylor, is to persuade Mr Blair to remove the Assembly's "law-making" powers, so permitting it to proceed along the lines of the Welsh model, while removing the need for an executive at all.
The attraction of this to some unionists is that it would meet Mr Blair's requirement for devolution in all parts of the UK, while removing the problem of executive powersharing with Sinn Fein yet retaining a full and equal role in a reduced structure for all parties.
In the current context, moreover, some of them argue this would be an appropriate response by Mr Blair to the SDLP's refusal to say it would proceed in government without Sinn Fein should the IRA default on decommissioning. However, even its advocates acknowledge that the Irish Government and the SDLP would be unlikely to run with this proposition. Which brings us back to base.
If legislative "fail-safes" fail to satisfy Mr Trimble, and the SDLP won't grant the alternative assurance that penalty will be exacted only on those who default, the last remaining hope is that in the next 48 hours Mr Trimble and his colleagues can be persuaded that London and Dublin have good grounds for believing the IRA intends to deliver.
Mr Blair has failed thus far. And Sunday's meeting between the Taoiseach and the UUP delegation was hardly plain sailing. However, Mr Ken Maginnis and a number of his colleagues are set to resume those discussions in Dublin today. Not for the first time in this process then - and perhaps appropriately - the prospects for good or ill appear to turn on a dialogue between the leaders of Ulster Unionism and the leaders of Fianna Fail.
Mr Ahern and Mr Trimble have placed much by their special relationship. We will know its true worth on Thursday.