Sir Reg Empey has launched a formal bid for leadership of the Ulster Unionist party.
Sir Reg has entered the Ulster Unionist leadership race
At a news conference, it emerged he has the backing of more than half the party's MLAs and MEP Jim Nicholson.
Sir Reg said the UUP was guilty of not listening to its supporters and vowed to change that if he became leader.
Former leader David Trimble resigned his leadership after the party lost all but one of its Westminster seats in the May general election.
Sir Reg, the former Northern Ireland enterprise minister, is an assembly member for East Belfast.
He said the Ulster Unionist Party's fightback was "only just beginning".
"The prognosis is good and the recovery will be full.
"We may have taken a standing count but this is a 15-round contest where guts and stamina will count for more than a lucky punch in the first round of a long and demanding cost."
Sir Reg said the party had failed to listen to its grassroots supporters.
"We were talking when we should have been receiving their messages," he said.
"We became disconnected from the concerns and anxieties of our supporters and potential supporters.
"Those days of high-handedness are over. On my watch, full weight will be given to the views of our supporters."
He said there would be "significant personnel changes in the broad leadership" of the party.
Younger members would be brought forward for positions of responsibility, he said.
The Ulster Unionist Council meets on 24 June to elect his successor.