Northern Ireland has had many recent days of destiny. Tomorrow undoubtedly is another for the leader of the Ulster Unionist Party, Mr David Trimble, and for the future of the Good Friday agreement.
If Mr Trimble emerges from the meeting of the Ulster Unionist Council with his political nerve and credibility intact the odds are considerably improved for the deal.
If he doesn't, the agreement and Mr Trimble's own political career would appear doomed. It's as serious as that.
The Ulster Unionist Council, ruling body of the UUP, has more than 800 members. About 700 of them are expected at the Europa Hotel in Belfast to decide whether to say yea or nay to the agreement.
Mr Trimble will enter the meeting conscious of the ghost of his 1970s predecessor, the late Brian Faulkner. On January 4th, 1974, Mr Faulkner appeared before the council to argue the case for accepting the Sunningdale powersharing arrangement. He failed by 427 votes to 374.
Five months later the Stormont government collapsed, destroyed by a combination of unionist and loyalist opposition. It was also the political end for Mr Faulkner.
Although it's now a hackneyed phrase, it's worth repeating that the SDLP deputy leader, Mr Seamus Mallon, has described the new agreement as "Sunningdale for slow learners". Generally, he directed that point at republicans, who also worked to destroy Sunningdale. Now, however, it's crucially pertinent to unionists.
Tomorrow's result will hinge on whether the greater unionist family - and 700 unionists is a pretty good poll of the general unionist view - has experienced a sea change over the past 24 years. It will tell whether what was previously unacceptable can now at least be tolerated or whether the "no surrender" of 1974 is the "not an inch" of today.
These recent days have witnessed a battle for the hearts and minds of the unionist family. The UUP supporters and opponents of the agreement have been arguing, and canvassing and lobbying, for their particular viewpoints. Each side admits that even at this late stage they can't call it.
What can be said is that Mr Trimble will face the council in a stronger position than did Mr Faulkner in 1974. While the 10member parliamentary party may be split on whether to accept or at least endure the agreement, he has the heavyweights with him.
On his side will be Mr Ken Maginnis, the party's combative security spokesman, who has the verbal ability to sway voters. Also there will be the deputy leader, the enigmatic and complex Mr John Taylor, ironically one of the politicians who, with Mr Trimble then playing a minor role, helped to destroy Sunningdale.
"If we'd lost John, we'd have no chance," said one UUP deal supporter this week. Although defeated for the party leadership in September 1995, Mr Taylor, who can be infuriatingly unpredictable, has been loyal to Mr Trimble in the crucial stages of the peace process.
Mr Taylor, a newspaper proprietor himself, took note of a Sun- day Business Post editorial decrying the agreement as "no deal for nationalist Ireland". He half-jokingly suggested that he might issue copies of the editorial to council members to help to persuade them they had won a good bargain for the Union. What may also be in Mr Trimble's favour is that in 1974 unionists had the assistance of the UVF and UDA paramilitaries in sabotaging Sunningdale. The opponents of this agreement don't have the mainstream paramilitaries to rely on.
Statistics can be unreliable, but it's interesting to note that in the first count of the UUP leadership election in 1995 pro-agreement Ulster Unionists - Trimble, Taylor and Maginnis - between them won 79 per cent of the 800 council votes.
The East Derry MP, Mr William Ross, and the Rev Martin Smyth - respectively opposed to and having great difficulty with the deal - won the remaining 21 per cent between them. If that result were to translate loosely to tomorrow's meeting Mr Trimble would be home and dry.
Here, though, it's important to remember that Mr Trimble, who won 36 per cent on the first count in the leadership vote in 1995, was elected as the unrepentant unionist "hero of Drumcree Mark I". A number of those supporters may now be opposed to the agreement.
No unionist likes the Good Friday agreement; the question is whether they will reluctantly tolerate it. There will be council members in the Europa who have definite views, and there will be others who are unsure or are wavering. Mr Trimble must win the waverers.
The Grand Orange Lodge on Wednesday expressed serious misgivings about the agreement but at least it resisted pressure from the Spirit of Drumcree group to declare openly against the deal.
During this week the pro- and anti-agreement unionist camps have been setting out their positions. The opponents of the deal argue that the Union is being damaged through the North-South bodies, through Mr Gerry Adams potentially serving in an Assembly cabinet with unionists, and through the early release of prisoners, the possible undermining of the RUC, and the absence of immediate decommissioning.
Mr Trimble's lieutenants, such as Mr Taylor and Mr Reg Empey, have responded by focusing on consent: that the incorporation of this principle in the agreement guarantees the Union.
They agree that early prisoner releases and commissions on policing and decommissioning may stick in the unionist craw, but that Dr Mo Mowlam would implement proposals in these areas "agreement or no agreement".
The alterations in Articles 2 and 3 which also acknowledge the consent principle are another selling point for the pro-agreement faction.
Council members will be told tomorrow that the alternative to accepting the agreement will be a new "turbo-charged Anglo-Irish Agreement", to quote Mr Empey earlier this week.
The results of the Irish Times/ Guardian poll may also help to persuade UUP supporters that the prevailing public mood accepts the deal. Unionists would also be conscious that rejection of this deal would play very badly with Tony Blair's massive majority Labour government and with the general British public.
Mr Trimble's presentation tomorrow will be vital. To win is important, but to win well would be the fillip he needs to undermine the internal opposition which, whatever the result, will not go away, and to strengthen his position against the external opposition from the Rev Ian Paisley and Mr Robert McCartney.
It would fortify him for the subsequent Assembly election in June in which Mr Trimble's people, rather than his UUP opponents' people, must do well to ensure the body can function properly.
Tomorrow is yet another daunting test for Mr Trimble. His nerve has held under severe strain, and there is no sign of any imminent vacillation. The challenge facing him is to bring party members past their understandable visceral antipathy to the agreement to the intellectual acknowledgment that what was achieved at Stormont on Good Friday may be as good as it gets.