Mark Stuart: Cable, once the people's favourite, now the forgotten man of coalition

And yet, not so long ago, he was the people's favourite, lauded as the only major politician who correctly predicted the economic crisis, invited on to every television sofa in the land to promote his excellent book, The Storm. An autobiography followed.

There was media speculation of him becoming a contestant on the BBC's Strictly Come Dancing programme. Not since Mo Mowlam received a longer standing ovation at the Labour Party Conference in 1998 than her leader, Tony Blair, had a politician been so popular.

Indeed, so plentiful was Cable's stardust that he was able to sprinkle some of it generously on to his inexperienced leader Nick Clegg, appearing with him at several events during the 2010 General Election campaign. Huge photos of Nick and Vince even adorned the sides of the Liberal Democrat battle buses.

And then, after Clegg's superb performance in the first of the Prime Ministerial debates came Cleggmania. Understandably, Cable was a little put out. The cartoonist, Martin Rowson, cruelly portrayed Cable as Geppetto, the old toymaker, bringing the innocent young Pinocchio (Nick Clegg) to life.

From that moment on, Cable was surplus to requirements. He was largely left out of the Liberal Democrat negotiations with the Conservatives that led to the formation of the coalition Government.

It became clear that Cable's sympathies lay elsewhere. We now know that, ever since the credit crunch began, Gordon Brown had regularly sounded out Cable on economic matters during a series of fireside chats.

During the immediate post-election period, poor Cable was being telephoned at ungodly hours by the Prime Minister, asking for his advice on the coalition talks between Labour and the Liberal Democrats.

In truth, Cable's heart has always been with Labour. Those ties date all the way back to 1979, when Cable served as John Smith's special adviser at the old Board of Trade in the dying days of James Callaghan's Government. Although he later converted to the SDP, he was still arguing for "good, constructive links with the current Government" several months after the Labour landslide of 1997 made such co-operation far less necessary.

Cable was therefore devastated at having to agree to a coalition deal with the Tories. The best spin that a politician renowned for his honesty could muster was that Britain faced a Greece-style situation in which a stable government needed to be formed. He was therefore putting the country's interests above narrow party advantage.

Since then, there has been no hiding the sullen disappointment on his face. Cable's popularity has subsequently dipped. When he appeared on Question Time in June, the Business Secretary made a perfectly lucid case in favour of early action against the deficit, and yet didn't receive a single round of applause.

Gradually, the critics of Cable have come out of the woodwork. So called "friends" point out that Vince is just another Ming Campbell: excellent in his comfort zone of economics (as Ming was in foreign affairs), but out of his depth elsewhere. They cite his hastily concocted Mansion Tax (which had to be revised) as evidence that he doesn't always get it right in the economic sphere. There are those who claim that Vince was such a doomsayer that he was bound to be proved correct after spending so many years predicting a recession.

Whatever the reality, the sad fact is that the Liberal Democrats are taking all the political pain in this coalition. While their party has slumped to 12 per cent in the opinion polls, the Tories are riding high above 40 per cent. Cable must have sensed this was going to happen: almost immediately on becoming a Minister, he gave up the deputy leadership of his party with indecent haste. Is this Act One in Cable's staged departure from the Liberal Democrats?

Not yet, anyway. Cable, despite his opposition in India last

week to the Government's planned quota on migrants, still harbours hopes of leaving his radical mark on this coalition by breaking up the banks. But will George Osborne at the Treasury let him?

Cable's predicament is analogous to George Brown who was asked by Harold Wilson to head up the Department for Economic Affairs (DEA) in 1964. Brown found out the hard way that it was no use dreaming up plans for restructuring British industry if the dead hand of the Treasury denies your ministry any real levers on power.

If anything, Cable's position is even worse than the ill-fated DEA, as his department is being severely squeezed by the Treasury.

So, for the moment, Cable resembles a rather stern economics professor, banished to a minor polytechnic, forced to watch while the best young boffins in the land conduct crazed experiments on the economy. But Cable is much more than that. He is a genuinely honest man who carries the hopes of large swathes of the progressive Left who still see him as the last remaining hope for radicalism in this new government.

If and when Cable decides that the radical flame has burned itself out, he will exit stage left. Others are bound to follow.

Mark Stuart is a political historian and analyst from York who has written the biographies of John Smith and Douglas Hurd.