Leading article: Three tricky tasks facing the third force in politics

The increasingly desperate struggle taking place in the Labour party throws the plight of the Liberal Democrats into stark relief. It demonstrates the disconcerting ease with which the third party in British politics, even in its major conference week, can be barged from the media spotlight. But it also highlights the opportunity open to the Liberal Democrats if they have the skill to exploit it. Politics is a zero sum game. With one of its two rivals in a state of confusion, the Liberal Democrats have a chance to offer themselves as a coherent and attractive alternative to the voting public.

The party therefore has three challenging objectives this week in Bournemouth. In what appears to be the overcrowded centre ground in British politics, they must acquire a more distinctive voice. The new policies that help them attract attention have to be consistent with the party's broader values. Finally, the policies must be credible. A failure to meet any of these conditions will almost certainly mean the Liberal Democrats lose seats at the next election rather than make more gains.

Under the leadership of Nick Clegg, the Liberal Democrats are close to meeting their first goal. In its scale and ambition, the sweeping package of tax and spending cuts being debated at the conference today is more daring than any programme being proposed by the other parties. The Liberal Democrats also stand out from the other parties in a range of policy areas. They are the most pro-European party and continue to put forward more radical green policies than either Labour or the Conservatives. The party is also the most committed to civil liberties. As ever, their plans for constitutional reform are the most radical.

This exposes the myth that the Conservatives have moved on to their terrain and stripped them of political purpose. In all these areas, David Cameron is in a different position, and even when the Conservatives appear to move close, it is with a degree of internal tension. Mr Clegg has also distanced his party from Labour with his declaration that the Government's experiment in social democracy has failed. Neither Charles Kennedy, with his background in the SDP, nor Sir Menzies Campbell, who stated openly that he was a left-of-centre leader, would have put it quite so starkly. There is still a dialogue between Labour and Liberal Democrat politicians, reflected in fringe meetings at both party conferences, but the era when the two sides worked closely together ended long ago.

Values and credibility

Yet there is some concern within the Liberal Democrats that in seeking to be distinctive, Mr Clegg has failed to meet the second objective. They fear his tax-cutting proposals challenge the party's values. The anxiety is understandable. At the last election, the Liberal Democrats called for a top rate of tax on high-earners partly in order to fund their spending proposals. Now they call for overall cuts in expenditure. But Mr Clegg has put his case astutely. He argues that his tax plans are a radical act of redistribution, a word that even Mr Brown never dares to deploy. He argues, with some justification, that the measures are consistent with his party's commitment to social justice. In addition, Mr Clegg leads in a changed political context, with the Labour government deeply unpopular and the Conservatives soaring in the polls. The thinking behind the previous Liberal Democrats' tax-and-spend policies was framed in the mid-1990s when the political situation was almost the reverse of what it is now. On these grounds alone, Mr Clegg is right to move in a new direction.

But there are doubts about whether Mr Clegg meets the third objective. Are the new policies credible? The details were framed before the severity of the economic downturn was clear and even then looked ambitious. Mr Clegg argues that the bleak news on the economy makes the case for tax cuts even more potent, but there is a strong counter-argument that these major fiscal reforms would be destabilising. It is also not clear that spending cuts are achievable on such a scale without damaging public services. Mr Clegg is fortunate to have Vince Cable as his authoritative Treasury spokesman. Mr Cable has some explaining to do this week.

This third objective is at least as important as the other two. If it appears that the Liberal Democrats have sacrificed credibility in an attempt to be more distinctive, voters will turn away. Whether they support Mr Clegg in substantial numbers at the next election is partly dependent on factors beyond his control. If the polls suggest that the election will be close, interest in the Liberal Democrats would soar.

There is not a lot Mr Clegg can do about the wider political context. Within the constraints of the current situation, and without an obvious issue such as the war in Iraq to rally support, he must make waves through other means. His proposals this week suggest that, over time, he will do so. Less than a year since he became leader, Mr Clegg has made a solid start. But the real work is only now beginning.