The Lib Dem leadership challengers have clashed over when British troops should be pulled out of Iraq.
In a BBC Question Time debate, Simon Hughes and Chris Huhne pushed for troops to leave by the end of 2006.
Mr Huhne said he knew from his time in business that deadlines were the best way of ensuring things happened.
But Sir Menzies Campbell, who does not want to set a firm deadline, countered, saying: "There are 8,500 lives at stake. This ain't business."
War march fears
Acting leader Sir Menzies also revealed he had held reservations about former leader Charles Kennedy going on the anti-war march in 2003.
Mr Kennedy's high-profile speech at the rally in Hyde Park, which ended the march, helped highlight the Lib Dems' opposition to the war.
But Sir Menzies, the party's foreign affairs spokesman, said he had been worried many people on the march were "viscerally anti-American", rather than just opposed to President George W Bush.
"My reservations were that if we weren't careful we would be associated with anti-Americanism," he said.
The 64-year-old was at the time having treatment for cancer so was unable to go on the march himself in any case.
Asked about how Britain could honourably leave Iraq, Sir Menzies said he wanted a full exit strategy rather than a deadline.
Power had to be handed to Iraqis and security ensured, he argued.
"Nothing would damage our interests more than if Iraq were to break up," he said.
"The consequences for the whole of the Middle East region would be quite shattering.
"We cannot stay there forever but we have a duty to do everything we can now."
'Part of the problem'
Mr Huhne said Iraq was different from Afghanistan because the British troops were associated with an "illegal" invasion of Iraq.
"We are part of the problem, not the solution," he said, saying many Iraqis did not want to see 8,500 British troops in their country.
"My experience in business is that if you don't set a deadline, things don't happen."
Party president Mr Hughes, who said his brother had served in Iraq, said troops should hand over power to Iraqis by the end of the year.
"If you do not say this is the year we come out then it could be an indefinite commitment because we don't know how long it will take for Iraq to be settled so it will be safe," he said.
The debate came after bookmakers made junior Treasury spokesman Mr Huhne favourite to win the leadership race.
The move followed a YouGov internet poll of 401 Lib Dem members in which 38% gave Mr Huhne support, 34% Sir Menzies and 27% Mr Hughes.
The poll was commissioned by former Tory MEP John Stevens, who is now a member of the Liberal Democrats and one of Mr Huhne's backers.
Mr Huhne said he was now the frontrunner but Sir Menzies' camp insists their canvassing shows a different picture and Mr Hughes said there were still thousands of votes up for grabs.
Mr Huhne became an MP only last year but said he had experience as a journalist and businessman, as well as an MEP.
But both his rivals said that knowing the inner workings of Parliament was useful for a party leader.