First off, though, in Campbell's defence: I'm not convinced by the "he's already 64, he has only one election left" argument. Last year both Tony Blair (by self-declaration) and Michael Howard (on age grounds) were clearly fighting their last elections as party leaders, and both got more votes than Charles Kennedy.
More widely, I think it's very unhealthy to expect party leaders to stay on for a decade as a matter of course - how many of us expect to be in our current jobs for that long? Four or five years should be the standard, and the party as a whole should be capable of generating sufficient talent to fill the top spot, and resilient enough to cope with elections every so often.
I know very little about Mark Oaten. A colleague tells me pleasing anecdotes of personal favours; an old friend tells me that he's done very well on Five Live. I think that he was very unwise to play the card of loyalty to Kennedy after that story was over (and I feel the same about Lembit Opik), and it's interesting that he couldn't even get seven MPs to sign his nomination papers having stuck his neck out.
Loyalty to both parties and leaders in politics is over-rated anyway. Those of us who are in any branch of politics - and I include myself, in both my professional role and my roles as a member of the Lib Dems and of the Alliance Party of Northern Ireland - are in it to change the world for the better. A political party, and its current leader, are only part of the means to that end, and as a political activist your support of either party or personality must be constantly judged against the question, "Is this going to help change the world the way I want it?" If your loyalty to either party or leader is stronger than the answer to that question, you are no longer a political activist but an adherent of a religious sect. Which is why I suspect that for both Oaten and Opik, their partisanship of Kennedy after the man himself had given up did them no favours.
Simon Hughes - well, what's not to love about Simon Hughes? Apart from the fact that he is known to turn up chronically late for meetings (Paddy Ashdown has a hilarious set of anecdotes about this in his memoirs), and that he is reputed to do as much constituency work as any two other MPs put together (or three, if one of them is George Galloway). I sat up and watched his extraordinary by-election victory back in 1983, and thrilled to every minute of it (the more controversial elements of the campaign were lost on me when I was 15).
And yet, and yet. There is the known character flaw of tardiness (and I voted last time for a candidate with a known character flaw), and I'm just generally not convinced that he will convert the voters rather than frighten them. Maybe I will be. I remember back in 1988 I was certain I was going to vote for Alan Beith until I opened the envelope with the election literature from the two candidates and realised that Ashdown might be risky, but would at least be interesting.
Which brings me to Chris Huhne. I know him vaguely and consequently like him from his time in Brussels as an MEP; he co-wrote a book with my former boss; the Oxford Mail is trying rather desperately to smear him as an extremist. I am rather impressed that despite his substantial economics background, he chose the environment as the main basis for his campaign launch, prompting some rather desperate me-tooism from the other candidates. Sure, he is not a household name; but be honest, who had heard of David Cameron twelve months ago?
And on the economics front: I'm aware of the suspicion generated recently by the publication of the Orange Book. I think its significance has been overblown. There is little prospect of a right-wing clique taking over the party a la Jorg Haider. I find it interesting that Liberator, which I take as a touchstone of the parts of the Lib Dems further (though not much further) to the left than me, responded to the Orange Book, not with the outright hostility which I remember the magazine taking to the leadership and the SDP in the Steel era, but by welcoming the fact that there was a debate at all (eg here and here; and Jonathan Calder, in his largely negative review for Liberator, singles out Huhne's contribution to it as "in many ways the most impressive piece in the book".
So, on balance, I'm a not very committed Campbell supporter, drifting towards Huhne. Having said that, as in 1988, I may just find that the candidates' own literature convinces me to change my mind at the last moment.