I agree with Iain that Charles Kennedy has shown good judgement in the past on many issues, not least when he came round to the anti-war position, and he is obviously well liked. It's clearly also true, as Iain says, that a leader who has lost the support of a substantial proportion of his own MPs and Cabinet can not continue, however just or unjust that may be.
I have harsher ideas. I think Kennedy's alcoholism has affected his ability and his judgement lately. Firstly he has missed or fluffed a lot of important public engagements, which reminds me of Vladimir Putin. For instance he didn't attend the last budget debate, which is one of the major events of the political calendar. Secondly - why doesn't he acknowledge what is obvious to everyone, that he can not continue to be leader? That is bad judgement, and its not listening to his advisers. I can't believe there is one person close to him, including his wife, who is not telling him to go. Yet he has not gone yet. He is humiliating himself.
And finally, the radical and aggressive steps that his colleagues are prepared to take, steps which risk damage to the party and their individual careers, convince me that they think things are very bad indeed. A lot of them see him day to day, a lot of them on telly were saying 'I hate doing this but I've got to'. We have to ask ourselves why they are so desperate. What have they seen in private that has been kept off camera?
I think drink is an anaesthetic, and people who are addicted to that anaesthetic coarsen their judgement and hamper their intellect. I think Bush is a malign example, and Kennedy is a tragic example.
The alcoholics I have known have often been intelligent people with lots of potential, all of them were damaged by it. All of them became difficult to be with, selfish, and obsessive. I don't have much experience with ex-alcoholics though, so I don't know how easy it is to turn around.