Gordon Brown is benefiting from the disarray among his party critics and potential successors. Their weakness has been highlighted by yesterday’s blunt intervention by Charles Clarke. Plenty of disgruntled, and even fatalistic, Labour MPs privately agree with him about the seriousness of the Government’s malaise. But he had hardly any public support yesterday. There are plotters, but not yet a credible plot. There is no sign of any leading figure willing to confront or challenge Mr Brown.

Of course, Mr Clarke’s comments and the renewed leadership speculation are an unwelcome distraction for Mr Brown as he tries to provide reassurance about the long-term strength of the economy. It blurs his message. But the current caution of the plotters also gives Mr Brown an opportunity to counter-attack, notably via the reshuffle expected in the next few weeks.

Moreover, there is no evidence that any successor could revive Labour fortunes. The new Populus poll for The Times, undertaken at the weekend, suggests that David Miliband would not necessarily do any better than Mr Brown. When voters are asked to imagine that Mr Miliband replaces Mr Brown, Labour is shown on 26 per cent, against 27 per cent now. The Tories are on 46 per cent, against 43 per cent, and the Liberal Democrats on 16, against 18, per cent. These figures are comparable, with an adjustment for voters reluctant to declare their preferences and a reallocation of some don’t-knows, though the normal voting intention question does not mention leaders by name (for more details see www.populus.co.uk).

There has been much debate about the value of such hypothetical questions. After all, Mr Miliband is still pretty unknown. In an ICM poll a month ago, little more than half of the public said they would recognise him.

Anthony Wells, of UK Polling Report, has cautioned against predicting the short-term effect of a change of leader, since so much depends on timing and circumstance. But Mike Smithson, of politicalbetting.com, has noted that questions naming an alternative leader, similar to that asked by Populus, proved to be prescient about Mr Brown before he took over. According to a dozen Populus polls, the Tory lead was about 4.5 points higher, on average, on the basis that Labour was led by Mr Brown rather than by Tony Blair. As Labour’s ratings have plunged, these questions have looked like an accurate forewarning of voters’ doubts about Mr Brown’s suitability as Prime Minister.

It is impossible to be sure how Mr Miliband or any other leader would perform. What matters is that there is no firm evidence that Labour would do either much better or worse under Mr Miliband. At present, that is useful for Mr Brown. It constrains his enemies and weakens any plots. He still has some cards. But in the face of continuing bad economic news, and interventions like those of Mr Clarke’s, what Mr Brown needs, above all, is time: for some, any, sign that the economy has bottomed out and that inflation, and interest rates, are on the decline, as they could be next year. This may not be enough electorally, but it is his, and Labour’s, only hope.

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