Liberal Democrat Charles Kennedy has called a leadership contest after admitting he has been battling with a drink problem.
He said he was determined to carry on as leader but wanted to give party members the "final say".
Mr Kennedy - who has previously denied a drink problem - admitted seeking "professional help" to beat the bottle.
He has faced growing calls to quit as leader with 11 frontbenchers reportedly saying they had lost confidence in him.
Deputy leader Menzies Campbell, who had been favourite to take over the top job, home affairs spokesman Mark Oaten and Northern Ireland spokesman Lembit Opik have all said they will not stand against Mr Kennedy.
Every candidate must be endorsed by 10% of the party's MPs
Whole party membership chooses leader
One member, one vote
Single transferable vote system - members list preferences and votes from least popular candidate reassigned to others until a winner emerges
Details of how the election will be arranged will be discussed in the next few days by the party's Federal Executive Committee.
However, Mr Opik told the BBC that he hoped no-one other than Mr Kennedy would put themselves forward - negating the need for a ballot.
Mr Kennedy is believed to have called a press conference to admit his drink problem "within an hour" of being confronted with detailed allegations by reporters.
In a personal statement at Lib Dem HQ in Westminster, he said he had not had a drink for two months and did not intend to have another one.
He said: "Over the past 18 months I've been coming to terms with and seeking to cope with a drink problem, and I've come to learn through that process that a drink problem is a serious problem indeed.
"It's serious for yourself and it's serious for those around you. I've sought professional help and I believe today that this issue is essentially resolved."
He added: "People close to me know that this has been a struggle and that for extended periods I've consumed no alcohol at all.
"As a matter of fact I've not had a drink for the past two months and I don't intend to in the future.
"I learned the hard way of the need to face up to this medical problem, one that is dealt with successfully by many others on a daily basis.
"I chose not to acknowledge it publicly before in this way because, if at all possible, I wanted to overcome it privately."
He said the issue has "understandably been of concern to my parliamentary colleagues" but said they had been "understanding and supportive".
Mr Kennedy has faced repeated calls for his resignation in recent weeks.
The BBC has learnt that just under half of Mr Kennedy's front bench team has signed a letter saying they no longer have confidence in him.
One of the signatories, environment spokesman Norman Baker, hailed the "brave" and "dignified" way Mr Kennedy had admitted his problem in public.
"I felt for him...it could not have been easy at all," he told BBC News 24.
He said he had signed the letter because he "felt matters were drifting" and the party needed to take action.
Mr Oaten - one of the men expected to challenge for the leadership - has confirmed to the BBC that he will not stand against Mr Kennedy.
He called on party members and MPs to get behind Mr Kennedy, saying they should "recognise and reward the courage he has shown".
Mr Kennedy was prompted to act after senior party sources told ITV News he had admitted a drink problem and sought treatment.
One source reportedly told the news organisation Mr Kennedy's "continued relapses" were damaging the party, and another claimed his private office was "lurching from one crisis to another, pulling him out of the abyss".
According to ITV four top party figures apparently cornered Mr Kennedy in his private office in 2004, and insisted he acknowledged his drink problem.
They succeeded in persuading him to admit his condition, and he has since been receiving "private" medical help, according to ITV.