One of Gordon Brown’s prime ministerial predecessors once famously remarked that ‘a week is a long time in politics’. These days, given the truncated chronologies of cyber communication, agendas and affections shift much more quickly. 24 hours usually does the trick.

For this reason, the general verdict among the pundits only a short while ago was that Mr Blair’s ‘long-farewell’, pitched towards the near eternity of 8 weeks, amounted to a serious miscalculation.

It’s probably slipped your memory by now, what with the ‘handover’ being old news too. But back in May they suggested that it would try people’s patience, destabilise the government’s parliamentary programme, and allow the opposition more time to train its attack dogs to sniff out Mr Brown.

The Independent newspaper, ever keen to find its next niche, wasted no time in launching a ‘Tony should go sooner’ campaign. But opinion polls indicated that most of the public sensed no such urgency. Then, inevitably, everyone got a wee bit bored with being bored, and the season of discontent began to peter out.

In fact, everybody now admits, New Labour’s strategists got it just about right. Their first aim was to diminish the repercussions of the recent local and national election results. That was uppermost in new diary boy Alistair Campbell’s mind.

And what better way to do it than with a succession of ruminations over Blair’s legacy, a kafuffle about who could (or should) challenge Brown, and a Big Brother-style deputy leadership eviction contest?

Next Labour wanted to get the Tories to shoot as many rounds as possible, just to see what they had in their arsenal. Sure enough, one minute nice Mr Cameron was telling us that Blairism was a disaster and the next minute he was being singled out as Tony’s natural successor.

That’s his dilemma in a nutshell – and it isn’t one which getting Blair out and Brown in a few days earlier than planned could ever hope to resolve.

Finally came the government’s ‘replacement message’ about a New Gordon – who would deliver both more of the same and something a little bit different, thus half-satisfying everyone except hardened cynics, entrenched opponents and the press corps.

This has since been confirmed with the clever twist over the International Development Secretary’s “coded attack” on US isolationism. First they put that message out, then the new PM gets to make reassuring noises at Washington – getting one big bird on each wing with two stones.

As for Cameron, just do the maths, argue the Brown strategists. And with nearly 5 out of 6 people in Britain still not voting for the official opposition, they continue to have a point.

This could all change, of course. But in case things start to slip there’s always the possibility of calling a snap October 2007 election in September, while Gordon is still riding high. (You read it first here.)

Political calculation is more about building on what you know than gambling on what you don’t. And what is known about the British electorate right now, when you analyse its details and discrepancies, is that everyone is favour of change so long as it doesn’t make too much difference.

For this reason the calculus of staying in power is rather different to the calculus of building or sustaining a different kind of political programme. This is the reality to be faced by those who hope that a Gordon Brown premiership can deliver a more economically redistributionist and socially progressive policy stance.

The fact is, the architecture of institutional political power dictates that the nearer you get to the summit the less air there is to breathe and the more you have to lose by making a wrong move.

Mr Brown, whose virtues include gritty resolve and substantial moral purpose, understands that well. Which is why, several years ago, he issued a salutary political challenge to churches, NGOs and world development lobbyists over a package of measures linking the G8 summit to United Nations’ anti-poverty goals.

What you need to do, said the then chancellor to the coalition of debt, aid and trade activists, is to deliver as visibly as possible the evidence of significant public support for change. This is what my colleagues and I require to substantiate the case for policies which will shift further resources to the very poorest.

The lobbyists took the hint and continued to campaign. The upshot hasn’t yet been a fulfilment of the majority of the pledges on poverty relief which they, and Mr Brown, fought for. But the case for public pressure to create the space in which official political manoeuvring can achieve more has been thoroughly established.

So too is the reality that shifting from one regime to another takes time, given that complex political processes designed for a plural environment are inevitably built as much on resistance as movement.

Meanwhile, so the Gospel suggests, faith can move mountains. In a world of uncertain allegiances, intransigent interests and uneven odds that sounds implausible, to put it mildly. But the improbable sight of Ian Paisley and Martin McGuiness sharing power in Belfast shows us that where a common will can be envisioned, a way can be found.

At its best, politics is the possibility of the artful.

This column is adapted from one that appeared in the recent issue of Third Way magazine.