Political correspondent Robert Merrick asks where did it all go wrong for a Prime Minister once hailed as a man ‘touched by greatness’ but now facing the possibility he will have to leave the job he craved all his adult life.

HE is a figure of ridicule – a cheap laugh for comics – teetering on the brink of a humiliating exit from the job he craved his entire adult life – perhaps in only a few days’ time.

Yet, less than two years ago, Gordon Brown was a political colossus, revered by supporters, feared by opponents and hailed even by right-wing commentators as a man “touched by greatness”.

Not since John Major went from General Election victor to economy wrecker in six months has a political reputation sunk so far, so fast.

So just how has it all gone so badly wrong for Mr Brown – and is there anything he can do to avoid being remembered as the worst Prime Minister in 50 years?

As Labour backbenchers decide whether to sign the now-infamous “Gordon must go” email, it is important to remember that no leader, or party, can defy political gravity for ever.

No Prime Minister could avoid a battering in the teeth of the deepest recession since the Thirties – and Mr Brown surely cannot be blamed for the apparent exposure of three Cabinet ministers at the centre of the turmoil – Jacqui Smith, Hazel Blears and Alistair Darling – as expenses cheats.

However, not even the staunchest Brown supporter could deny their man’s central role in his own downfall.

So, is his lack of charisma to blame? Is it his chronic indecision, his lack of a popular touch, the failure to communicate – or the existence of a “dark side”?

Of course, Mr Brown does lack charisma – at least, set against Tony Blair or David Cameron – but that was seen as a plus when we were all sick of the former PM’s grin.

Far more damaging is the inability to act swiftly and decisively when faced by a crisis such as the expenses scandal and the outpouring of public fury it provoked.

It is a trait he developed during his long years at the Treasury, when it made perfect sense to consider all options at length, before choosing one.

We see it in the way Mr Brown is most comfortable thinking about the long-term at G20 meetings – or when he condemned the “totally unacceptable”

Hazel Blears, only to fail to strike – instead, leaving the knife lying around for her to plunge into his back this week.

That inevitably revived memories of the “election that wasn’t”, when he let the country know he was planning a poll, only to pull back at the last – exposed, not only as a schemer, but as an incompetent one.

It was similar scheming, to ensure a march into No10 unchallenged by any Blairite rival, that explained the disastrous decision to axe the 10p tax rate.

In a single stroke, to curry favour across the Labour Party, the soon-to-be Prime Minister threw away a richlydeserved reputation for being on the side of the needy.

Of course, when he did act decisively – in the much-lampooned YouTube video, pledging an expenses crackdown – it backfired, exposing that inability to communicate effectively.

And do not underestimate the damage done by the Prime Minister’s “dark side”, laid bare by the Damian McBride affair, in which his hand-picked aide targeted opponents with poisonous smears.

Those who have known him throughout his career remark on Mr Brown’s weakness for “surrounding himself with nasty people”, who have sworn undying loyalty.

Nor, of course, can he escape all responsibility for the economic mess we are in.

But, ironically, just as the economic gloom starts to lift with evidence that Britain returned to growth last month, Mr Brown is in a much-deeper, political mess.

Of course, he is famously resilient and has wriggled out of a similar crisis already, when his dynamic response to the near-collapse of international capitalism last year briefly restored his public standing. Can he do it again?

Whatever Labour’s pollratings, regardless of the Cabinet ministers who have walked out, Mr Brown is still far from out for the count.

There will not be a formal leadership challenge, because party rules prevent it, and the backbench revolt is nowhere near as far advanced as the one he saw off last year.

That leaves the Cabinet. If Mr Brown can reshuffle his senior ministers without a walkout by figures untainted by expenses shame he could yet survive until an election next year.

But then he will meet the voters – who seem to have long since decided that the job Mr Brown craved for a lifetime is the one he is simply not up to doing.