Dave's useful idiots

Of all the many insults hurled at Gordon Brown during his troubled premiership, perhaps the most wounding was the one delivered by the then Lib Dem acting leader Vince Cable during Prime Minister's Questions in November 2007.

"The House has noticed the Prime Minister’s remarkable transformation in the last few weeks from Stalin to Mr Bean," he told guffawing MPs.

But three years on, the now former Prime Minister may well have permitted himself a wry smile or two at the transformation in Mr Cable's own political fortunes.

In the space of less than 12 months, he has gone from Saint Vince, the most trusted politician in Britain, to a man now widely regarded as little more than a useful idiot for the Tory-led coalition.

Some of it is purely by virtue of his having swapped the luxuries of opposition for the harsh realities of power, at a time when the government was bound to be unpopular whoever was in it.

Yet even within that context, Mr Cable has demonstrated an unusual ability to shoot himself in the head.

His 'declaration of war' on media baron Rupert Murdoch, after being honeytrapped by a pair of female undercover reporters into speaking too frankly about his government role, has backfired more spectacularly than a turbo-charged boomerang.

The end result was that Tory culture secretary Jeremy Hunt this week nodded through a deal which will make Murdoch the dominant player in UK print and broadcast media, with even more financial clout than the BBC.

But if Dr Cable's ambitions in the field of media policy have been well and truly thwarted, the same would seem to apply to his conduct of regional policy.

After the election last May, Dr Cable put it about that he was going into bat to ensure that those English regions that wanted to would retain a region-wide political and economic voice.

Such a stance was, after all, in keeping with a Lib Dem election manifesto that promised to "reform" regional development agencies rather than abolish them wholesale as the Tories' did.

At one stage, Dr Cable was privately telling regional political leaders that the RDAs in the North East, North West and Yorkshire would be effectively be preserved, under the new guise of Local Economic Partnerships.

On the face of it, it hardly seemed Dr Cable's fault that this did not end up happening, and that communities secretary Eric Pickles prevailed in his determination to dismantle the entire regional political infrastructure.

Yet a Freedom of Information request by the Newcastle Journal has since revealed that, far from putting up a huge show of resistance, Dr Cable met his Tory counterpart just twice to discuss the issue.

In terms of the bigger picture, the RDA abolition and the Murdoch bid for BskyB point to a wider political reality - the inability of the Lib Dems to influence major policy decisions taken by this government.

And if proof was needed that this is now a widespread perception among the public, the result of Thursday's Barnsley by-election, which saw the party slumping to sixth place, surely provides it.

For some of us, the result brought back memories of those dear, dead days when world-weary Lib Dem activists used to sing a song called 'Losing Deposits' on the last night of their annual conference, to the tune of 'Waltzing Matilda.'

But for Dr Cable and his fellow Lib Dem ministers, there will be no such wallowing in nostalgia for more innocent political times.

Evidence is mounting that membership of this Coalition government is destroying the Lib Dems as a political force – possibly permanently.

How much more of it the party can take before it is obliged to go its own separate way will continue to be the defining question in British politics over the coming months.