Liberal Democrat leadership hopeful Simon Hughes has said the race is "wide open" after a poll of party supporters indicated he has taken a healthy lead.
The winner is set to be announced on 2 March
Bookies had almost ruled out the party president's chances after admissions he misled voters about his sexuality.
Economics spokesman Chris Huhne became favourite to pip veteran acting leader Sir Menzies Campbell to the post.
But a YouGov poll for the Sunday Times newspaper puts Mr Hughes on 34%, Sir Menzies on 21% and Mr Huhne on 13%.
However, one in three of the party supporters surveyed remained undecided.
And among the wider public 18% backed Sir Menzies to succeed Charles Kennedy, while 16% supported Mr Hughes.
Former journalist and MEP Mr Huhne, who was only elected as an MP in May, polled 10%.
YouGov surveyed a representative sample of 1,617 adults, online, on 9 and 10 February.
Mr Hughes told BBC News: "It is wide open.
"I have always thought it was wide open.
"I have always thought I could win.
"I can win; and that is why I am trying and making sure that I can."
But he added: "The party members will decide.
"The only poll that counts is the poll on the day."
Lib Dem MPs' chairman and Hughes Campaign Committee head Paul Holmes said the poll "reflects all the feedback Simon has been getting as he travels round the country meeting party members".
"I am increasingly confident Simon's message of freedom, fairness and sustainability is seen by members as the best for the future direction of the party and, just as importantly, is one that resonates with the British public," he added.
But one of Mr Huhne's supporters, MP David Howarth, criticised the polling of the party's supporters rather than members, who are eligible to vote.
"This poll is like asking people in Chippenham to predict the outcome of the election in Dunfermline.
"The only poll carried out among members who are voting in the leadership election... shows that Chris is clearly ahead," Mr Howarth added.
"However, we are not taking anything for granted."