Mr Jeffrey Donaldson has finally severed his connections with the Ulster Unionist Party, further reinforcing the position of the Rev Ian Paisley's Democratic Unionist Party as the dominant force within unionism.
The defection means that in any new executive, the DUP, under the d'Hondt system of apportioning posts, could be entitled to four ministerial positions, compared to only two for each of the three other main Northern parties.
It was an acrimonious parting. Mr Donaldson predicted that if the Ulster Unionist Party did not topple Mr David Trimble as leader, then the UUP faced "political collapse". Fellow Assembly members Ms Arlene Foster and Ms Norah Beare also resigned with Mr Donaldson.
"If the UUP does not change leader and policy then the DUP will do to the UUP what Sinn Féin is doing to the SDLP," he said.
Mr Donaldson said last night he will discuss with the DUP over the Christmas holiday whether he will join the party. He indicated, however, that he would join, which would give Dr Paisley 33 Assembly seats against 24 for the Ulster Unionist Party.
This would give the DUP a majority of nine in the Assembly, whereas when the last Assembly was elected the UUP had a majority of eight over the DUP.
Moreover, such a move would leave the DUP with six Westminster seats, compared to five UUP seats. Two of these seats are held by the Rev Martin Smyth and Mr David Burnside, who do not take the party whip, but who so far are remaining within the UUP.
Mr Donaldson acknowledged to The Irish Times last night that the logic was that he would formally join the DUP. Were the executive reinstated in the current circumstances, with Mr Donaldson remaining independent, unionists and nationalists would be entitled to five ministerial posts each - not including the posts of First and Deputy First Ministers, which would be held respectively by the DUP and Sinn Féin.
But were the rebel Ulster Unionists to sign up to the DUP, the DUP would be entitled to four ministerial positions, with the UUP, Sinn Féin and the SDLP entitled to two each, giving unionists a 6-4 ministerial majority in any reformed executive. This could serve as an incentive for the DUP to reach an accommodation with Sinn Féin.
Mr Donaldson said he would be joining the DUP's negotiating team in the New Year review of the Belfast Agreement. This will considerably strengthen the DUP's hand in these talks. "Unionist realignment is the only option now. Otherwise we could be facing the prospect of Sinn Féin as the largest party after the next Westminster elections," said Mr Donaldson.
He said it was not impossible that Dr Paisley and Mr Gerry Adams as leaders of the two largest parties could strike a deal acceptable to both unionists and nationalists.
"In politics anything can happen, but republicans will have to recognise the reality that David Trimble is not capable of delivering agreement. They must also recognise that if they are to do a deal with anti-agreement unionists, they must make the moves that are required."
Mr Trimble's response was temperate, although some pro-Belfast Agreement UUP sources welcomed Mr Donaldson's defection. "Jeffrey's decision is a matter of regret but it has not come as a surprise," said Mr Trimble.
The resignations crowned a year of huge political gains for Dr Paisley. He too predicted the collapse of the UUP. "This is without doubt a momentous decision that will deal a hammer blow to the Ulster Unionist Party, leaving them little more than a rump of unionists badly out of touch with the views and aspirations of the majority of the unionist community," he said.