Who wants to be a deputy leader?

Talking of internal Westminster dogfights, the race for the deputy leadership of the Lib Dem MPs may turn out to be more fun than weary Westminster observers might have imagined.

One minor mystery about the post is what exactly is its purpose?

Back when they were in opposition, and dropping leaders at an alarming rate, the Lib Dem deputy leader could reasonably expect a moment or two in the sun.

Vince Cable made a bit of a mark when his party ousted Sir Ming Campbell and he stood in while Nick Clegg and Chris Huhne fought their leadership battle; remember his quip about Gordon Brown's transformation "from Stalin to Mr Bean"?

When Dr Cable took up a seat in the Coalition cabinet, he resigned the deputy leadership, arguing that it should not be combined with a ministerial post - and Simon Hughes, one of the Lib Dems' longer-serving luminaries took over.

But no-one imagined that had Nick Clegg departed, it would be he who took over as DPM.

On his (mildly surprising) appointment as a justice minister, in obedience to Cable's Law, he resigned in his turn.

Hence the current vacancy.

Now, I'm told, the two contenders are Solihull street fighter Lorely Burt and Burnley bruiser Gordon Birtwistle, both relatively junior figures. (It's rumoured that the former Scottish Secretary, Michael Moore, toyed with running, but was discouraged from on high.)

What role might they perform?

There's already a mother confessor/agony aunt for troubled or unhappy MPs, in the shape of Annette Brooke, the chair of the parliamentary party.

And party president Tim Farron is the head of the party in the country, the preferred guest on the Lib Dem rubber tofu dinner circuit.

One possible function might be to speak on behalf of the Party as distinct from the Coalition, touring the studios to present an unvarnished Lib Dem view as the election approaches.

To be sure, Mr Farron can do that, but maybe another voice might be helpful. But (in obedience, again, to Cable's Law) it looks like a job for an ex-minister.

Former defence minister Nick Harvey is said to be utterly uninterested, which leaves former health minister Paul Burstow as a possible from the ranks of ex ministers.

Alternatively, one of the more bumptious new wave of MPs might pop up.

Tessa Munt, Julian Huppert, Martin Horwood?

But there seems to be a rising anxiety that the Libs could end up putting the wrong person in the wrong role...

Meanwhile the exodus of the Lib Dem Commons elders continues, with Chief Whip Don Foster joining Sir Alan Beith, Sir Ming Campbell, David Heath and Sir Malcolm Bruce in the departure lounge.

Given that the Libs might get to choose six or so peers in the dissolution honours list, I doubt they'll all make it onto the red benches.

One of the criteria the leadership use to choose, is how hard they work to guarantee their seat is inherited by a Lib Dem, so expect no slackening of constituency effort...