The Week in Politics: Growing up, but challenge for Lib Dems is to convince us their juvenile ways are left behind

Charles Kennedy has a vision of a typical voter: fortysomething, probably middle income and middle class, worried about their elderly parents, their own pensions and how to prevent their children being weighed down with debts when they leave university.

Charles Kennedy has a vision of a typical voter: fortysomething, probably middle income and middle class, worried about their elderly parents, their own pensions and how to prevent their children being weighed down with debts when they leave university.

Sound familiar? The good news is that the Liberal Democrats have a package tailored just for you: free personal care for the elderly, which already exists in Scotland; a £25-a-week increase in the state pension for the over-75s and the abolition of university tuition fees.

The goodies would be funded mainly by a 50 per cent higher top rate of tax on earnings above £100,000 a year, affecting only 1 per cent of the population, and raising £4.3bn. For good measure, the party would also replace the council tax with a local income tax.

This programme will be trumpeted during the Liberal Democrats' annual conference starting tomorrow. It's not exactly new, though most voters won't know about it yet.

Mr Kennedy's mission is to convert mid-term protest votes on Iraq into solid support for bread-and-butter policies at the general election expected next May.

Next week's conference in Bournemouth is both an opportunity and a threat. It will provide a platform for closing an "information gap" about the party's policies. But it could expose a "credibility gap" about whether the plans add up. In the past, the media has not paid much attention to Liberal Democrat proposals, but that is changing as the party becomes an increasingly attractive alternative to the two main ones.

There won't be a series of new policies at the conference. There will be a concerted attempt to convince us that the party's plans are fully costed and credible. This is overdue. Some of the "savings" the Liberal Democrats identify are at best optimistic and at worst bogus.

The party has grown up under Mr Kennedy but it has not yet outgrown its juvenile ways. It does not road-test its policies properly before launching them, in a way that a serious party must. So the coming week will be a big test. It will also be a big challenge for Mr Kennedy himself. The party does have its strongest frontbench team for many years, but many people will probably vote for a leader rather than a party next year. So Mr Kennedy will have to be on form. There are some in his own party who want the leader to take more risks and provide more oomph. They fear the tortoise-like Mr Kennedy lacks the X-factor of his hare-like predecessor Paddy Ashdown, who was in a hurry to get into power and thought the best way was to get a couple of Liberal Democrat bums on cabinet seats. The Kennedy approach is more plodding, and not driven by soundbites and headlines.

Commentators like me will doubtless spend much time analysing whether Mr Kennedy's party has shifted an inch to the left or an ounce to the right. He is relaxed about this because he senses that the voters have moved on from such labels. The political marketplace is in a state of flux, with voters much more likely to shop around, and so the Liberal Democrats have an unprecedented chance to sell their wares. Iraq is a bridge too far for many Labour supporters and they may not come back - at least not by next May.

Labour, which has virtually ignored the Liberal Democrats because they took votes from the Tories, will now attack them in a more systematic way. A swing from Labour to the Liberal Democrats in Labour-Tory marginals could cost Labour scores of seats. Recent polls, which show both Labour and the Tories in the low 30 per cents, suggest the two main parties are heading for a very low combined share of the vote by historical standards. Labour strategists, I am told, reckon they'll be lucky to manage 37 per cent at the election - hardly much of a mandate.

The lack of love for the big two parties may help the Liberal Democrats break through their glass ceiling at previous elections, when many judged them a "wasted vote" because they could not win power.

In the past, I have doubted Mr Kennedy's claims that Britain has a "three party system"; I have called it "two-and-a-half party politics". Well, I reckon it's now up to two and three quarters. The Liberal Democrats still have a long way to go. But, at present, they are the only major party going in the right direction.

a.grice@independent.co.uk