Steve Richards: A change in leader won't help the Lib Dems... they are entirely at the mercy of events

The best result for the party would be a Labour win with a small overall majority

What would happen if the Liberal Democrats replaced Ming Campbell with a younger leader? The answer is they would get another leader facing exactly the same nightmare. The problems afflicting the Liberal Democrats have little to do with leadership. The party is in trouble because of the wider political context. The background may change in the coming months. Whether it does or not is beyond the control of the Liberal Democrats' leader, whether young or old.

New leaders of the two bigger parties are guaranteed a honeymoon. For a time, their parties give them a remarkable degree of leeway to make their mark. If they are successful, that space expands. If they stumble, their freedom to act as they wish contracts quickly. Gordon Brown is using his honeymoon to define himself against the past, or rather past perceptions of his political character. For now, his party tolerates the symbolic games he is playing with Margaret Thatcher and others to show that he is a non-tribal leader on the centre ground.

Similarly, David Cameron made use of his early freedom by highlighting the environment and wooing left-of-centre figures from the media and elsewhere. The fact that Mr Cameron's strategy has produced only mixed electoral success means he is more constrained now. Even so, he will do all he can to seek out what he regards as vote-winning terrain, the so-called centre ground of British politics.

The insecure need of Mr Brown and Mr Cameron for the comfort zone of the centre presents the Liberal Democrats with an almost impossible short- term difficulty. Their position is dependent on what the other parties are doing. Their leaders do not get a guaranteed honeymoon.

Normally, they suffer the opposite. Campbell's two predecessors languished in the polls early in their leadership and came fully to life only once they had hit upon a clear sense of political purpose. In both cases external events came to their rescue.

For Paddy Ashdown it was Labour's fourth election defeat in 1992 that gave him a political project. The fear of eternal opposition led a few senior Labour figures to contemplate working more closely with the Liberal Democrats. When Tony Blair became leader in 1994 Ashdown seized the moment and moved closer.

One of the myths about the relationship is that wily Blair took the gullible Ashdown on the biggest ride in British politics. In reality, Ashdown got a fair amount from his intense political friendship. Most important of all, his closeness to Blair made the Liberal Democrats seem more important than they really were at a time when Labour was commanding the political stage. He gave the third party momentum at a time when it could have been swallowed alive.

On a crudely political level, Charles Kennedy was more fortunate. The war against Iraq gave his leadership and his party a distinctive position on the overwhelming issue of our times. For once, at a national level, it could be truly noted that if the Liberal Democrats did not exist it would have been necessary to invent them. Without them the House of Commons would have been almost fatally out of touch with the electorate, as Labour and Conservative MPs competed to hail Blair for his political courage at a time when he was being dangerously weak. The third party had a noble cause.

Now the situation is more fluid and its purpose is unclear. Three parties claim to be green. Labour and the Conservatives distance themselves from Iraq. There is even a degree of common ground about the level of public spending required, at least in the public debate between the parties. That is the political situation in which Campbell leads his party. Any successor would struggle too. Being younger does not in itself give the third party a clear purpose.

There are, though, three reasons why the Liberal Democrats should remain relatively calm. The first relates to policy. At the moment, Labour is too scared to debate policy openly, to ask what it means to be a left-of-centre party seeking a fourth term. That is why Brown places so much emphasis on consensual symbolism. To their credit, the Conservatives have debated policy openly. In doing so, they revealed deep divisions. In the meantime, the Liberal Democrats dare to say what other parties, especially Labour, do not.

It is a limited role, but a significant one. They are the advance guard in the battle of ideas. Alone of the leaders, Campbell puts the case for progressive taxation, arguing that high earners should pay more. He also dares to argue why the European project benefits Britain, the only leader to put a positive case. In terms of the environment and civil liberties, they have a more fully worked out programme than the other parties.

This will not get them very far in the immediate future. To rediscover a national sense of purpose they depend on other factors to come into play. If the Brown honeymoon ends, Labour will lose patience with his dances to the right. If Cameron fails to deliver on his early leadership agenda, as he seeks to reassure the right, the Liberal Democrats can hope to be beneficiaries. But above all, the outcome of the next election will determine their fate.

There is a widespread assumption that Campbell and other ambitious Lib Dem MPs hope desperately for a hung parliament. That is not the case. There is no doubt that Campbell would be more comfortable working with Brown and Labour in a formal or informal partnership than he would with the Conservatives. Unlike Kennedy, he describes himself openly as a left of centre politician. He is a friend of Brown's and admires his performance so far as Prime Minister. Most of all, he wants to achieve a change in the voting system for the Commons, a reform that Brown has not ruled out.

But Campbell knows it would be impossible to justify working with Brown if Labour loses its overall majority. He would be propping up a leader who had suffered a major reverse at his first general election, an impossible contortion. Therefore, the best result for the Liberal Democrats would be a Labour win with a small overall majority.

In such circumstances, Brown would have the legitimacy to remain Prime Minister, but would be leading a fragile government. Almost certainly, Brown would seek to cement his vaguely defined progressive consensus by working with the Liberal Democrats. Campbell would have at least the space to negotiate with Brown. Once more, there would be a fizz of excitement for a third party at a national level.

The Liberal Democrats must wait on events with their fingers crossed, a dull role but an unavoidable one in the current fluid political situation. The question of leadership is irrelevant. They have held one contest that made them look ridiculous. Forcing another one so soon afterwards would make them appear more absurd, even before a single candidate had uttered a word.

s.richards@independent.co.uk