The defining moment for Mr David Trimble and Ulster unionism has come. Faced with the decision of half of his parliamentary party to resign the whip early yesterday, Mr Trimble has moved quickly to announce his intention to expel the three MPs - Mr Jeffrey Donaldson, Mr David Burnside and the Rev Martin Smyth - from the Ulster Unionist Party.
He has called a special meeting of party officers for Thursday to set the expulsions in motion. Mr Trimble is to confront his critics head-on at a time when, Mr Donaldson maintains, the party is divided down the middle on the future of the Belfast Agreement.
Irrespective of the outcome, Mr Trimble had to take some step to win back the initiative. Mr Donaldson may have heightened expectations about his options when he said that he would "consider his position" in the event of defeat at the Ulster Unionist Council last week. He has not defected to the Democratic Unionist Party. But his resignation of the whip from the UUP parliamentary party, along with two senior colleagues, has seriously damaged Mr Trimble and called into question his authority to deliver on any deal in the future.
Mr Donaldson wants to have it both ways. With his motion to reject the Joint Declaration defeated, albeit by a narrow margin, by the 860-member UUC last week, he decided to resign the whip with immediate effect and remain within the party. The president of the UUC, Mr Smyth, and Mr Burnside joined him. They took this course to leave them free to act in what they consider the best interests of their electorate and the broader unionist family.
The net effect of this development is to lower the status of the UUP from the fourth-largest to one of the smallest parties in Westminster. Mr Trimble may well have won the vote within the UUC. He may have the support of a majority of members of the prorogued Assembly. In strictly unionist terms, however, he is the leader of a much-diminished force in the Mother Parliament to which unionists give their allegiance.
At first glance, Mr Trimble is taking a courageous step in moving to expel Mr Donaldson, Mr Smyth and Mr Burnside from the party. He equates the resignation of the whip as a resignation from the UUP. If he succeeds, he will strengthen his authority to refashion the UUP as a pro-agreement party. He can proceed with a confident and coherent position to broker a deal on devolution and decommissioning.
The UUP has been the necessary force for stability in Northern Ireland throughout the 30 years of the Troubles. With all its imperfections, it has been the only pro-agreement unionist party. There is a profound worry, however, that Mr Trimble is playing for the highest stakes now. There must be a concern whether a bloody purge of dissidents in the UUP will check the rise of the DUP and the anti-agreement vote in the next Assembly elections. There is no guaranteed outcome to the current crisis.