Andrew Marr tried manfully this morning to lasso the ether that is Nick Clegg. He was successful up to a point….but whenever the LibDem leader briefly took physical shape as a slippery eel to be speared, he was gone in a puff of smoke once more – to that political dimension where there is no reality, and no oxygen in which truth can breathe.

One gets the impression Marr doesn’t like our newest political star. When Clegg tried his boyish charm, saying “This is like a rehearsal for the Leaders’ debates”, the BBC man glared at him and said merely, “Well, if you choose to interpret my questions that way, all well and good”. I also had the feeling that on the migrants’ amnesty (where for once, Clegg is showing a degree of bravery and commonsense) Andrew was deliberately obtuse about what his interviewee meant.

But the Scot we hate to love was far more convincing when he forgot his own politics for a minute or two, and took the Slog’s line on what deal Nick really does want to do. On supporting or not supporting Labour after the election, for instance, Marr tied him in knots.

Will you refuse to support Labour if they lose the popular vote, he asked. Yes, said Clegg. What if Brown had gone, asked Marr. Um, err, well, said Clegg – and then rapidly changed the subject.

At last – too late in my view – Andrew Marr raised the on-off love affair the LibDems seem to be having with real PR.

Is PR non-negotiable, he asked. I think it’s unavoidable, Clegg replied. So it’s non-negotiable, Marr repeated. It’s unavoidable, said Clegg. Do you think you’re replacing Labour as the progressive force in British politics, Marr asked. I think the Labour Party is looking increasingly irrelevant, Clegg hedged. So how can you replace them and embrace them, Marr demanded. Once again, Andrew’s own political preferences were showing here: but all the same, Nick Clegg looked deeply uncomfortable.

It’s all very well excusing Clegg with all this ‘yes, but he’s got a job to do’ tripe. We’ve reached the point where political leaders really shouldn’t be allowed to get away with “I don’t what to get into what if”. These are our votes they taking unto their breasts, to use as poker stakes: we have a right as electors to know what they would do with them – because that might change the way we vote in the first place.

My problem with Clegg isn’t just that he’s a lightweight Eurocrat no more likely to tackle our deficit problem than the other two. My issue with the guy is that he keeps saying he’s a different kind of politician – out to end the Westminster stitch-up. But if Labour bowls along with a promise of Alternative Vote as the new electoral system, Nick Clegg will grasp that approach. Not only is it not PR in any shape or form, it would also be deeply unfair to all other Parties not as closely aligned as Labour and the LibDems: what is that, if not an even more disgraceful stitch-up?

Two more weeks to go, in which anything could happen. My own contacts and enquiries suggest that at least two very significant things will happen. So yes, this election is more exciting than we thought it was going to be. But is it more encouraging? No: if anything, it’s more depressing.