Mrs Daphne Trimble, wife of the Ulster Unionist leader, has failed to be selected to fight for the Lagan Valley Westminster seat against Mr Jeffrey Donaldson.
Following the selection meeting in the constituency on Thursday night, Mr David Trimble yesterday endorsed the successful contender, Mr Basil McCrea. The businessman from Hillsborough, Co Down, won the nomination by a margin of almost two to one.
The seat will be a hotly contested one following the defection of Mr Donaldson to the DUP in January.
He topped the poll in last November's Assembly election with 14,104 first preferences when still an Ulster Unionist.
He later joined the DUP along with fellow Lagan Valley Assembly member Ms Norah Beare and Ms Arlene Foster from Fermanagh.
The Ulster Unionists put on a united front yesterday with Mr McCrea meeting Mr Trimble at party headquarters in Belfast to discuss the "strategy and the agenda for taking Lagan Valley constituency back into Ulster Unionist hands".
Mr Trimble described Mr McCrea as "the right man for the battle ahead" and emphasised the importance of winning Lagan Valley in next year's anticipated Westminster election.
The constituency was held by the former UUP leader Lord Molyneaux prior to his retirement.