Sheffield Hallam MP Nick Clegg has become the second candidate for the leadership of the Liberal Democrat party.
“We cannot go on testing the patience of the British people,” he told an audience in his constituency at the launch of his campaign.
“We must come together now and make a long-term commitment to British Liberalism. We must step up or risk falling back for good.”
Former party leader Lord Paddy Ashdown is supporting Mr Clegg’s candidacy, as is Steve Webb, who was rumoured to be considering his own bid for the leadership.
Chris Huhne announced his candidacy on Wednesday, just two days after the shock resignation of Sir Menzies Campbell.
In an interview with the BBC on Tuesday the 66-year-old Scot said he took the decision alone, and explained he had been irritated and frustrated over standing down.
“Irritated because of the quite extraordinary concentration of trivia which seem to surround leadership – people write articles on what kind of socks I wear,” he said.
“Frustrated at not getting the opportunity to lead the party in a general election, and I think our policies and our principles and our values would have been right at the very centre of the political agenda.”
Nominations for his successor open today and close on 31st October.
Mr Clegg, 40, has been an MP since 2005 and so could not have voted for most LGBT equality legislation.
He voted in favour of outlawing discrimination on the grounds of gender reassignment but was absent from votes on the Sexual Orientation Regulations.
Nominations close on 31st October.
Lib Dem members will be sent ballot papers on November 21st, and they must be returned by 15th December.
The winner will be announced on Monday 17th December.