This party conference season may well be the last before the next general election. Whether the date of the hustings is a few weeks or a few months away is a matter of speculation. The Opposition parties, in particular, need to be primed for the possibility of a poll sooner rather than later. That prospect will cast its shadow over proceedings at the Liberal Democrat assembly which started yesterday in Brighton.

That election is likely to be a more difficult experience for the party than the past two campaigns. Tony Blair has left the scene and the controversies which were associated with him personally have inevitably lost some of their bite. David Cameron is a more emollient figure than was Michael Howard or William Hague before him. The two major parties thus appear unlikely to drive voters into the arms of the third party. This has been reflected in opinion surveys which put the Liberal Democrats consistently below the 22 per cent of the national vote which they secured in 2005. Conference speakers this week may talk in terms of how many more seats the party can win; leaders worry about how many MPs they may lose.

This reality explains much about the complaints directed at the leader. The details of the Populus poll for The Times published today do not make comfortable reading. The percentage of the public who agree with the thesis that “The Liberal Democrats are basically a protest vote party because realistically they have no chance of ever forming a government” is, at 69 per cent, the highest since this claim was first presented five years ago. Furthermore, 63 per cent of all voters and 67 per cent of those who would back the Liberal Democrats believe that the party will have a chance of making an impact only if the current leader is replaced by a younger and more charismatic individual.

These are bruising findings and will hardly make for a more benign conference. It is not clear, however, whether any alternative to Sir Menzies Campbell would have done better. In many respects, his efforts have been underestimated. They have also involved a paradox.

Conventional wisdom has it that the leader has retained his command over foreign policy but struggled in the domestic arena. While this might be broadly true at Prime Minister's Questions, the opposite could also be noted. Whereas Sir Menzies has sought to make his party look again at its old assumptions on tax, spending and the public services, he has made no such demand for second thoughts about its instincts in the international sphere. His only notable innovation here, to call for a referendum not on the EU Treaty but membership of the European Union itself, seems to be uncharacteristically eccentric.

Sir Menzies was always destined to be a transitional figure whose role was to make his party a more plausible coalition partner for power and to bring on a younger generation of MPs who are willing to acknowledge that Britain and the world have changed. He has made some progress in that drive but should be bolder. It is entirely possible that in 12 months’ time he will be a former, rather than the serving, leader of his party. His legacy may not be an increase in seats or votes but it can be a rise in credibility. “Go back to your constituencies and prepare to do better in 2011 or 2012” might not be the most inspiring line that a party leader could offer to conference delegates. Yet, in truth, the task for the Liberal Democrats has to be to look to the future.