In the course of the past three decades or so, leaders of first the Liberal Party and then the Liberal Democrats have been respectively charged with and acquitted of conspiracy to murder, obliged to confess to an extramarital liaison with a secretary and driven from office because of excess alcohol consumption. Compared with all that, Sir Menzies Campbell could contend that one set of particularly poor opinion poll results was not much to be concerned about. Such complacency would, however, be reckless. The numbers we report today are dreadful. The Lib Dems have not been at such a low ebb in years and the leader’s personal rating is now at a level not witnessed since the traumatic days when Iain Duncan Smith headed the Conservatives. Put crudely, the bulk of the electorate appears to have decided that it preferred Charles Kennedy drunk to his successor sober.

The most damning figures, though, come from Lib Dem supporters themselves. By a margin of 54 per cent to 39 per cent, party voters assert that Sir Menzies should be replaced rather than retained. That is a damning figure, and he will be damned if there is not a significant change in his performance and ratings. What is worse still for the Liberal Democrats is that the numbers may become more awkward if Gordon Brown makes a reasonable success of his first few months in office. They have already lost some of their former supporters to David Cameron as he seeks to reclaim the centre ground. They could lose another group back to Labour as Mr Brown draws a line under old disputes such as the Iraq war and university top-up fees. The party made much noise in advance of the elections this month about fighting on two fronts, against Labour in the North and the Tories in the South. The results of those contests imply that the Lib Dems are in retreat in both regions.

To an extent, there is not much that Sir Menzies can do about his situation. No initiative that he undertakes would have the same impact as those of a new prime minister. Nor is it clear that the party would instantly do better if it opted for Chris Huhne, the runner-up in last year’s leadership ballot, or Nick Clegg, its home affairs spokesman, who is the other serious prospect. To drop two leaders in little more than 18 months would hardly inspire confidence in the party. It would instead invite factionalism and mockery.

But Sir Menzies cannot allow matters to drift on into the party conference season and from there to Christmas. The more intelligent of his internal critics concede that he is running the party machine far more efficiently than his predecessor and that he is presiding over a policy review that should produce a more coherent election manifesto. The difficulty, nevertheless, those same critics contend, is that none of this is visible to the voters. They can be excused for regarding the Liberal Democrats as less of a party than a void that has nothing new to say to the country and whose leader is decent but weak.

Sir Menzies has to project strength quickly. If he has fresh ideas, he cannot afford to wait for months before revealing them. If he intends to take on his activists over policy, he must signal that immediately. He also has to commit himself wholeheartedly to improving his presentation skills. Mr Brown has shown in the past few days that a mediocre performance can work a little magic on stage. Above all else, Sir Menzies has to ask himself whether he has the necessary fire in his belly for the task in front of him. If not, then it is but a matter of time before his leadership is extinguished.