The race to replace Sir Menzies Campbell as Liberal Democrat leader has begun, as MPs start sounding out colleagues about potential bids.
Sir Menzies quit after 18 months in charge, saying leadership speculation was impeding the party's progress.
Party president Simon Hughes denied he or deputy leader Vincent Cable had "wielded the knife" against the leader.
The early frontrunners to succeed him are Nick Clegg and Chris Huhne, but as many as seven are considering running.
Nick Clegg, the current home affairs spokesman, said he needed time to talk to his wife Miriam and "close friends" before deciding whether to stand for the leadership.
16 October - Nominations open
31 October - Nominations close
21 November - Ballot papers sent out
15 December - Deadline for completed ballots
17 December - New leader announced
"Events have been very, very sudden. They've taken me by surprise, many people by surprise," he said.
He added that he had spoken to Sir Menzies, who he described as behaving "with extraordinary dignity and integrity".
Chris Huhne has not said if he will stand - but sources closed to him have told the BBC he is likely to make a statement on Wednesday.
On Sir Menzies' surprise resignation on Monday, he told the BBC: "I think it is a sad business that there have been, I think, quite a lot of ageist comments about Ming. Obviously it is a very private decision and one that he took carefully."
Among others who have told the BBC they are sounding out colleagues about whether they should stand are Steve Webb, who is in charge of writing up the party's election manifesto, and Birmingham Yardley MP John Hemming.
Steven Williams, MP for Bristol West, previously supported Chris Huhne but said he would be talking to him, Nick Clegg and Steve Webb later before making his mind up.
"I think all three of them have been ringing around colleagues to see whether they can muster enough support in order to mount a credible leadership bid. This is going to be a different sort of election from what we went through about 18 months ago."
Mr Hughes, who has stood for the leadership twice before, has ruled himself out of this contest.
He told the BBC the party owed Sir Menzies "a huge debt of gratitude", and said he had taken "his own counsel", rather than being forced out.
But Lib Dem MP Mike Hancock is among those who believes Sir Menzies was hounded out by members of the party.
"Why should he have to take some of the back-biting from people who couldn't say it to his face?," he said.
The party's chief executive and elections expert, Lord Rennard, denied he had been forced out, telling the BBC: "There wasn't a plot, Ming made the decision his own way yesterday."
He said it was a "real tragedy" for Sir Menzies that a general election campaign had not been called for November, as he expected the party to have done "extremely well".
The official announcement was made on Monday evening by Mr Cable and Mr Hughes, who said Sir Menzies had taken the decision in the "interests of the party and of Liberal Democracy".
Former Lib Dem leader Lord Ashdown described Sir Menzies' resignation as "a selfless act by an honourable man who put his party first".
"I regret his decision to go, although I think it was probably the right one," he told BBC Radio 4's Today programme.
The peer said he had planned to meet Sir Menzies on Tuesday to discuss his future.
"I was going to say to him: 'Look, Menzies, it's going to be quite tough for you to continue until an election in 2009 but the one thing is very clear and that is when you go, go on your own terms and go when you want to go'. He beat me to it," he said.
The official contest to select a successor has already begun, with the winner due to be announced on 17 December.
Speculation had been growing about the Lib Dem leadership, particularly since Prime Minister Gordon Brown decided not to call an early general election - and indicated he may not do so until 2009 at the earliest.
And talk of replacing Sir Menzies as leader appears to have been stirred by poor opinion poll results - the latest being an ICM poll in the Sunday Telegraph which suggested Conservative support at 43% with Labour on 36% and the Lib Dems on 14%.
Since he became leader Sir Menzies, 66, has repeatedly had to defend himself against accusations that he was too old to lead the party.
Data not available for September 2006 and February and March 2007.