Nominations have closed in the Liberal Democrat leadership race.
The contenders are lining up with their backers
Deputy leader Sir Menzies Campbell, party president Simon Hughes and new MP Chris Huhne are the three contenders.
They face the task over the five week contest of rebuilding the party's reputation after recent controversies which have seen poll ratings slide.
Ahead of the nominations closing the ex-Lib Dem election candidate Adrian Graves switched to join David Cameron's Conservative Party.
Mr Graves says he made his decision before the twin "catastrophes" which saw Charles Kennedy and home affairs spokesman Mark Oaten resign.
Mr Kennedy left after admitting to a drink problem and Mr Oaten quit the front bench at the weekend after revelations of an affair with a male prostitute.
Lib Dem party members have until 1 March to vote in the leadership race.
Candidates had to be nominated by at least seven MPs and 200 party members from at least 20 different constituencies.
25 January - nominations close
6 February - ballot papers sent out
1 March - vote closes
2 March - result announced
Mr Graves stood unsuccessfully as a Lib Dem candidate in Suffolk West in 1997 and 2005.
He said he was defecting because of the "fundamental shift in both the direction and political atmosphere" of the Conservatives.
Mr Graves told BBC Radio 4's Today programme the Tories were the only realistic option for "regime change".
"The majority of British people recognise that a fourth term of a Labour administration, a weaker one, potentially shored up by perhaps a Simon Hughes-led group of Lib Dems is the nightmare scenario," he said.
More to come?
The 57-year-old public relations consultant claimed that up to three Lib Dem MPs might be considering defecting.
And Harold Elletson, a former Tory MP who now chairs the Lib Dem foreign affairs forum, said many people, including MPs, were worried about the direction Lib Dems might take.
Asked whether he might be prepared to return to the Tories, he said it would depend on where Mr Cameron took the party.
"I and many others have been impressed by what we've seen so far and would no doubt be prepared to consider all sorts of things in the future," added Mr Elletson.
But a Lib Dem spokesman said: "Mr Graves was an unsuccessful candidate at the last general election.
"If Mr Graves truly believes in civil liberties, in the environment, and in social justice he will be sadly disappointed by the Conservative Party."
A spokesman for Mr Hughes also rejected Mr Graves' criticisms.
"The position we are taking is that Lib Dems are the only party to have consistently have fought for our environment, civil liberties and fair taxation," he said.
Mr Hughes had not ruled out listening to other parties if there was a hung Parliament - but only if there were promises of a fairer voting system, added the spokesman.
All three candidates will debate on a special edition of Any Questions? on BBC Radio 4 at 2100 GMT on Wednesday.
Treasury spokesman Mr Huhne told the BBC's Daily Politics he was glad the bookmakers' odds on his chance were "moving nicely in the right direction".
The former City economist also attacked Labour's Treasury team for having a "cloth ear" on economic issues because none of them had any business or market experience.
At prime minister's questions, acting leader Sir Menzies suggested the hundreds of thousands of deaths in the conflict in Darfur was a sign of failure.
Tony Blair told him the international community was failing people in Darfur but the UK was pressing for the African Union peacekeeping force to come up to full strength.