Praise has been paid to Charles Kennedy's contribution as Liberal Democrat leader after he stood down following his admission of alcoholism.
Mr Kennedy had been party leader for six years
It comes after 25 MPs delivered an ultimatum saying they would refuse to serve on the Lib Dem frontbench.
Mr Kennedy said he was standing down as leader with immediate effect.
Deputy leader Sir Menzies Campbell said the party would be forever in his debt but the SNP said Julius Caesar was better treated than Mr Kennedy.
Sir Menzies confirmed he would be standing for the position of leader of the party.
Standing down, Mr Kennedy said the interests of the party had to come first.
He said his successor should be appointed as soon as possible to fight the May local elections, and pledged his support as "a loyal backbench Liberal Democrat MP".
There were "serious internal political issues to address further and to resolve", he warned.
Sir Menzies, speaking outside his home in Edinburgh, commended Mr Kennedy for his "dignity and courage" and for his achievements as leader of the Lib Dems over the past six years.
He said: "Under his leadership the party has advanced to its best position for 80 years and the party will forever be in his debt.
"Today we must wish him and his family well.
"As deputy leader I will be assuming his responsibilities with immediate effect and over the next 48 hours will obviously be consulting colleagues. But I can confirm today that I intend to be a candidate in the leadership contest which is to follow."
BBC Scotland political editor Brian Taylor said that Mr Kennedy departed with dignity, despite the difficult circumstances of the past few days.
He said: "To be blunt, he had lied to his party and to the public when he insisted, repeatedly and in terms, that he did not have a drink problem.
"But Mr Kennedy was also pushed out because critics feel he had failed to deal sufficiently with the policy and strategy choices facing his party."
Scottish National Party leader Alex Salmond said: "Charles Kennedy confronted his problems and appealed for support, but his MPs have responded by knifing him in the front.
"Julius Caesar was better treated by Brutus than Charles Kennedy by his colleagues.
Mrs Kennedy expressed pride over her husband's record
"Whatever else, the Liberal Democrats have now lost their reputation as the 'nice party' in politics."
Scottish Lib Dem leader Nicol Stephen said he was "very sad" Mr Kennedy's leadership had ended this way.
He said: "There is no doubt in my mind that Charles Kennedy was the key reason why the Liberal Democrats did so well in the last two general elections."
Former Scottish leader Jim Wallace paid tribute to "one of the party's most successful leaders".
"I am proud of a friend who has shown such dignity and courage, and who has contributed so much to the cause of liberal democracy," he added.
As Mr Kennedy arrived back at his south London home with his wife Sarah she also expressed pride at what he had achieved.