This will be the year Charles Kennedy breaks the mould of British politics

The Liberal Democrats' New Year poll ratings really are putting the fear of God into the Conservative Party

Of all the party leaders arriving back in the Commons for Prime Minister's Questions today, it will be Charles Kennedy who will be displaying the happiest post-Hogmanay glow. And, although his jollity will be checked by the death of Roy Jenkins, he can feel upbeat in the knowledge that the first poll of the New Year puts his Liberal Democrats on 25 per cent – their highest rating for nearly a decade.

Mr Kennedy can also claim Lord Jenkins's mantle as much as – some would argue more than – Tony Blair, and it is fair to say that the Liberal Democrat leader has probably been under the spell of the late peer for all of his political career. It is often forgotten that Mr Kennedy originally won his Ross and Skye constituency in 1983 under the pure colours of the SDP, founded two years earlier by the Gang of Four. To this extent, Mr Kennedy was the first of the new generation of today's centrist politicians to have been an original child of Lord Jenkins's brand of social democracy. And he has literally grown up, throughout his 20 years in Parliament, with Jenkins to hand as a personal mentor.

Not for Mr Kennedy the need to explain away a past dalliance – as with Mr Blair – with the extremism of the Labour Party; no embarrassing membership of CND or even an old election address committed to withdrawing from Europe. As every member of the SDP or Liberal Party who was elected in the 1980s can testify, their entry into politics by means of the third party cannot simply be dismissed as a cynical career move to gain ministerial office. For the putative politician concerned with climbing the greasy pole, there have been easier options of realising ambition by joining Labour or the Tories.

So it is only fair to credit Mr Kennedy with principles, rather than personal ambition, when he stood as a 23-year-old for a Tory seat, finding himself subsequently elected to Westminster, and having never even been to London before. But now he does have to show that he has an ambition. And while it may still be preposterous to imagine him as Prime Minister, he can be forgiven if, this week, he has occasionally dreamt that the hand of destiny could yet touch him in the future. And even if the dream is moderated to riding around in the official limousine of the Leader of the Opposition, he could still be in Lord Jenkins's "breaking the mould" territory.

There have been many false dawns, but something about the recent run of polls suggests an exciting ride for Mr Kennedy this year. For the last decade the Liberal Democrats have punched above their weight at general elections. In 1997 their share of the vote was only 17.3 per cent – lower than in 1992 – and only barely increased to 18.2 per cent in 2001. Yet in terms of seats they have made a breakthrough and really are putting the fear of God into the Conservative Party.

But a really dramatic advance has now shown up in the pre-Christmas ICM poll and the New Year poll by Live Strategy, which show the Liberal Democrats on 24 and 25 per cent respectively. Never before, when Labour governments have been in power, have the Lib Dems registered such a strong showing. Often, with an outgoing Tory government, they have profited from disaffected Tories voting for them – indirectly contributing to the election of a Labour government. As soon as the Wilson and Callaghan government of the 1960s and 1970s hit bad times, it was always the Tories, rather than the Liberals who profited.

So far, this showing has happened without Mr Kennedy having to do very much. With the Tories in such a parlous state and the Government displaying serious mid-term blues, the Lib Dems should expect to do well without much effort. Some have attacked Mr Kennedy for a lazy approach, while others have argued that there is a deliberate plan – to have no strategy and simply feed off public disaffection with the other two parties. But Mr Kennedy is not lazy – relaxed maybe – and has accurately picked up on the current anti-politics culture of public opinion. This explains why he is right to eschew the demands from some to overdo the daily diet of screaming and shouting, and also accounts as to why he scores so heavily in poll ratings on personality, compared to both Tony Blair and Iain Duncan Smith.

The better their poll ratings are, and there are clear signs of a real trend being established here, the greater will be the scrutiny to which Mr Kennedy and his party will be subjected. For the time being, therefore, there is much to be said for not "peaking too soon". The really big advance will come if the Lib Dems are ever on level pegging with – or overtake – the Tories. In fact, this may well matter more than winning by-elections. In the past, it has been these one-off events that have provided the engine of electoral advance. But the statistical prospects of a by-election victory in this Parliament are slim, because of the dramatic reduction in the average age of Tory MPs after the 1997 election.

And here is a dilemma for Mr Kennedy should his current opinion poll advance be sustained. Such a scenario would certainly hasten the demise of Iain Duncan Smith. If this resulted in the election of Kenneth Clarke as Tory leader, it is a fair bet that the Tories may halt and reverse the Lib Dem advance. Certainly the type of Tory voter who likes Mr Clarke is precisely the voter who would otherwise be tempted to vote for Mr Kennedy. So Mr Kennedy needs the Tories' current leadership in place at the next general election, with Mr Clarke remaining well out of the picture.

On policy, the Liberal Democrats are still at the drawing-board stage. Again, this is no bad thing. The better they do in opinion polls the more they are prey to the charge of being all things to all men. In the past they hid behind the "extra one penny on income tax" as a way of paying for their unsustainable wish-lists. Now they have to recognise that Gordon Brown has taken many extra pennies with no discernible benefits. There are signs that the voters may not be willing to pay for the public services, which will test the Lib Dems previously profligate tax-and-spend tendencies.

But there is one area of pure, principled opposition to the Government, on war with Iraq, that could be Mr Kennedy's strongest opportunity, and where he has the field to himself. If he has the courage to be the respectable leader of the peace party, he could have a "good war". There is no enthusiasm among the public for conflict. But even if it comes to a war that is won, there will be many among the public who will respect a party leader who asked the tough questions throughout the conflict. Some say that Mr Kennedy may be worried about being on the "losing" side if the war is "won". He should not worry about such considerations. He could win a much bigger prize for sheer consistency and principle – thereby laying claim to be the genuine inheritor of the lustrous Jenkins mantle.

mrbrown@pimlico.freeserve.co.uk