Lib Dem leadership hopeful Sir Menzies Campbell has insisted that at 64 he is not too old to take on the job.
Sir Menzies said he would ban the words "hung parliament"
He told BBC Radio 4's The World at One he would stay in the role "for as long as I'm able to do the job properly".
Sir Menzies, the Lib Dem acting leader and foreign affairs spokesman, said he would have "no problem" with still being leader at the age of 72.
Simon Hughes and Chris Huhne are the other candidates. They face their final contest hustings on Thursday evening.
'It is appropriate'
Sir Menzies compared himself with 69-year-old US senator John McCain, who has said he may contest the presidency.
He said: "If 69 is appropriate to offer yourself to lead the United States, then I think 64 is appropriate to offer yourself to lead the Liberal Democrats."
Sir Menzies, the oldest of the three candidates, added: "I would like to be Liberal Democrat leader for as long as I am able to do so.
"If that took me to 72, I would have no problem with that."
Asked whether he could consider joining a Conservative-led coalition in the event of a hung parliament, Sir Menzies said: "The party's objective must be to get the maximum number of votes and the maximum number of seats.
"If I were our leader, I would ban the words 'hung parliament' from the Liberal Democrat dictionary."
Party members have until 1 March to select a new leader, with the result expected the next day.
Mr Hughes, the party president, appears on The World at One on Friday. Treasury spokesman Mr Huhne was featured on Wednesday.