Yes, er well no, hang on, or, sorry.” Thus Nick Clegg under a little light questioning on television a few days back, moments after he started an answer with the fateful words: “Let me be very clear...”

Now, “Yes, er well no, hang on, or, sorry” may not up there with “Time for a Change” or “Labour isn't Working” but I think it might make a rather good slogan for Mr Clegg's leadership campaign. Certainly it would be a pretty good summary of what we have seen so far.

You see, I've read a large number of admiring comments about Nick Clegg and articles insisting that he must be the Liberal Democrats' man. But now the Lib Dem contest is a few weeks old, I feel I can't be alone in beginning to wonder — is he really that good?

It's easy to see why the admiring articles have been written. Mr Clegg is decent, engaging and good company. He is clearly a very intelligent man and it is always a pleasure to discuss a political issue with him. As a result, political journalists, me included, have been convinced for some time that he would be an excellent choice and that the moment of his accession could not come soon enough. And on one thing we were undeniably right. He will make a better leader than Ming Campbell.

However, being described as a better leader than Ming Campbell is, as one of my friends put it, like being called a better violinist than Abu Hamza. It's not enough upon which to build a career as a professional musician. If Mr Clegg is going to rebuild his party, now languishing in the polls, he will have to do much, much better than that.

Take his performances on television. It is his quality as a performer on the box that is most often cited when his claims to the leadership are advanced. Perhaps we weren't watching closely enough. Since the contest has begun Mr Clegg has been hesitant when interviewed, exasperated when criticised and petulant when attacking his opponents. If Gordon Brown is the clunking fist, Nick Clegg is more the stamping foot. In the private conversations that have so impressed journalists, Mr Clegg is always cool and collected. In public it doesn't take much for him to lose it. Lose it in a polite Liberal sort of way, of course, but lose it nonetheless.

Then there's policy. Chris Huhne angered his opponent by accusing him of changing his mind on the issues. But I am less concerned with Clegg flipping than I am with him flopping. I hoped he would be an exciting new force in politics, helping to change the debate in this country by siding with the centre Right on the need for market-based reform of public services. Maybe he still will be, but he has spent most of the campaign defending his position with activists by insisting that school vouchers are off the table, as is radical NHS reform. His room for manoeuvre, should he be elected, has been reduced.

And I worry, too, about his steadiness under fire. He seemed to be firm about Trident. Chris Huhne would dump it, Nick Clegg would keep it. A true multilateralist, he. But debating on Question Time on the BBC, Mr Clegg announced that both he and Mr Huhne wanted to get rid of Trident. The difference was only that they differed about how to dispense with it — unilaterally or after negotiation. With that appeal to activist sentiment, he reduced his policy to incoherence. How can you negotiate successfully, when you have already said you want an end to Trident? His position on Trident may not be that important; his ability to withstand pressure from his party is. And, given that we could have a hung Parliament after the next election, so is his ability to understand the principles of negotiation.

Yet the most important question over the Clegg campaign is this — does he have a direction for his party, a story?

A comparison is constantly made with David Cameron and, through him, with Tony Blair. But both Cameron and Blair campaigned for the leadership of their parties as change candidates, delivering a bracing message to party members and indicating clearly that a break with the past was needed.

Nick Clegg became the media favourite for the leadership partly because he, too, appeared to be the change candidate. He was fêted as the head of a small but talented group with a strong sense of the sort of party they wanted. The Liberals would move back to the centre, challenge David Cameron, use their third-party status to take brave stands on policy. Activists would resist, but a clear mandate and charisma would force them to come along.

What's happened to all that? Clearly you don't want to frighten the voters during an internal election, but if you want to be the change candidate you have to talk about it at least a little. You can't simply spring out from behind the sofa after the campaign is over and shout: “Surprise!” When asked on television to outline the differences between them, Mr Huhne and Mr Clegg both avowed that basically there weren't any. Really? What's the point, then?

It may seem surprising to say after all this that I like Nick Clegg, have always rather admired him and that I haven't (supposing that he cares) quite given up on him. But his leadership campaign has been a terrible disappointment.

So let me put it like this, Nick. The Liberals have been a shambles and you know it. As Lady Bracknell might have put it, losing one leader may have been unfortunate but losing two looks very much like carelessness. Your party has lost nearly half the vote it had at the last election. Policy has lacked a cutting edge. The Lib Dems need a strong leader with a clear platform ready to challenge the members, making it radical, making it serious.

Either you decide, right now, that you will be such a leader and stop being cautious. Or don't bother. “Yes, er well no, hang on, or, sorry” is just a waste of everyone's time.

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