The Ulster Unionist Party's sole remaining MP has ruled herself out of the race for the party leadership.
Lady Sylvia Hermon said she faced a dilemma as her husband is ill
Lady Sylvia Hermon, the MP for North Down, said she had decided not to go forward in the contest to succeed David Trimble.
Lady Hermon cited family commitments - her husband, Sir John, suffers from Alzheimer's disease.
She regretted the disappointment her decision would cause to many people who had encouraged her to go forward.
In a statement released on Tuesday evening, Lady Hermon paid tribute to all those who had supported her.
"I greatly regret the disappointment my decision will cause, not only to colleagues who have been so generous in their support, but also to the many people throughout Northern Ireland and beyond who have so enthusiastically encouraged me to enter the leadership race," she said.
"They will, I trust, come to understand the rightness of my decision in the present circumstances."
In an earlier interview with the BBC, she had said she needed to think of her husband, the former chief constable of the RUC.
She insisted that she would "not let him down in his hour of need".
UUP leader David Trimble announced his decision to stand down after the party lost four of its MPs in the Westminster election.
Mr Trimble, the former first minister in the suspended Stormont Assembly, lost his Upper Bann seat. The UUP now has one MP, compared to nine Democratic Unionists.
Lady Hermon has been an MP since 2001 when she took the North Down seat from the UK Unionist leader Robert McCartney.