The chairman of the Ulster Unionist Party executive, Lord Rogan, said he had reacted with a mixture of surprise and sadness to the Rev Martin Smyth's leadership bid.
Lord Rogan, seen by many as a source of counsel and stability amid the growing internal ructions besetting the UIster Unionists, says he has also been left wondering about the long-term strategy of Mr Smyth and his supporters.
"Here is a man who has said on two occasions publicly that he was going to be standing down in the near future," Lord Rogan said. "He will be 70 by the time the next election comes. So is he going to be a caretaker leader if he wins? What exactly are their plans?
"I am disappointed and saddened by what has happened. The way things were going perhaps this was not entirely unexpected. But there is still astonishment when it happens, when the decisionto run is taken by someone in the twilight years of his political career."
Many observers of the Northern Ireland political scene believe Mr Smyth is a "stalking horse", and others may step in to challenge David Trimble in the future.
Lord Rogan, a former chairman of the constituency association of South Belfast, where Mr Smyth is an MP, continued that it was "no shock" that dissident Ulster Unionist MPs, such as William Ross and Willie Thompson, would be supporting the challenger. Nor did he seem perturbed by the assertion of the young Ulster Unionist Council chairman, Dr Philip Weir, that all but one of his 34 delegates would vote against Mr Trimble.
However, Lord Rogan was sceptical about Mr Smyth's claim that he had a "50-50" chance of winning unless other candidates came forward.
"That is highly optimistic," he said. "I have no doubt whatsoever that David Trimble will continue to lead the Ulster Unionist Party with vigour and determination. I will support him in all his endeavours and so will the majority of the party."
Other high-profile party members who have come out publicly in favour of Mr Trimble include Ken Maginnis MP, and ministers in the suspended executive, Sir Reg Empey, Michael McGimpsey and Dermot Nesbitt.
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