Is it so outlandish to envisage Charles Kennedy as Prime Minister?

Only the Liberal Democrats as a party speak for the wide swath of public opinion with deep concerns about war

No one has set out the parameters of what should take place in today's Commons debate on Iraq better than the last Prime Minister to lead Britain into war in the Gulf. Last week, in a BBC interview, John Major brutally eclipsed Iain Duncan Smith by setting out with stunning clarity at least some of the questions that any opposition has a patriotic duty to ask the executive about the impending war: What is the exit strategy? Who will replace Saddam? How long can coalition troops expect to stay there? Will Iraq break up? It's a testament to extraordinary political times that of all the leading frontbenchers taking part in the debate only Charles Kennedy and Menzies Campbell of the Liberal Democrats will be free to ask them, as they will undoubtedly do today.

In his statement yesterday, Mr Kennedy went further, questioning the basis in international law for the objective of "regime change". Maybe this, and the gibe about US "imperialism" were a response to criticisms that his party has not been even more robust in challenging the Blair strategy on Iraq. But the fact remains that it is the only one of the opposition parties to have done so at all.

A number of senior Tories have a deep unease about their present leader's stand, which will doubtless surface today. For the Tory leadership is pledged to back President Bush however unilaterally he acts. It would only oppose Tony Blair if he were to refuse to back action that did not have the sanction of the UN.

Thus only the Liberal Democrats as a whole party speak for the wide swath of public opinion with deep concerns about the prospect of war. The fact that Menzies Campbell seems to be broadcasting more frequently just now than his Tory counterpart, Michael Ancram, is precisely because he is the only opposition frontbencher you could imagine as Foreign Secretary – and in Campbell's case it's very easy to imagine – who actually has something different to say from Jack Straw.

In the inescapable terms of low politics, therefore, Iraq represents a real opportunity for the Lib Dems. For now, at any rate, Mr Campbell's words can hardly fail to be more interesting than Mr Ancram's, or Mr Kennedy's than Iain Duncan Smith's. Indeed, in mere party terms, the Iraq issue, sombre as it is, has become a kind of metaphor for the once-again fashionable proposition that just perhaps the Lib Dems could eclipse the Tory party in a much more permanent way than they will today. There is heady talk, not all of it discouraged by Mr Kennedy, that when the electorate finally tires of New Labour it could be to the Lib Dems that they will turn, that it is no longer completely outlandish to imagine a Kennedy premiership, not after the next election, but conceivably the one after that or the one after that.

It isn't churlish to have a healthy scepticism about all this. It's true the Tories have defied the predictions of many commentators, this one included, by staying so unpopular for so long. The strange death of Tory England isn't, perhaps, quite as fantastic a thought as it once was. It's true, too, that the dashing of Paddy Ashdown's hopes of a lasting Lib-Lab alliance cannot fail to renew interest in what the Lib Dems can achieve as genuinely independent third party.

On the other hand, the variables do not need much spelling out. Let's suppose that Tony Blair does go ahead and call a euro referendum next year – a prospect surely made that much likelier by the re-election of Gerhard Schröder. (Because the German Chancellor has every reason to be grateful to the British Prime Minister's public intervention on his behalf he may help to smooth the path towards British euro entry by helping to ensure that Europe's forthcoming constitution is not too integrationist).

There must be at least a chance that the Conservative Party, in a post-EMU world, will shed its rebarbative europhobia and broaden its appeal to middle opinion as it did with such success for so much of the last century. That said, however, it is sensible to match a strategy to how things are rather than how they might be.

Charles Kennedy's Liberal Democrats are in better shape to capitalise on Conservative weakness than they were a year ago. The decentralised, locally responsive, and in part locally funded, consumerist public services envisaged in the MEP Chris Huhne's important policy document do not create a promised land. But they strike a chord. Structures do matter – Tony Blair, no less, believes that an error of the first Labour term was to think they did not and that only nationally and centrally-set standards did.

Mr Huhne's document – which is also cheerful about the use of the private sector in delivering public services – is not some dramatic shift to low tax, free marketism. Or even quite the abandonment of the "cul-de-sac" of being to the left of Labour celebrated by the MP Mark Oaten, one of the party's brightest young Turks, in a newspaper interview yesterday. But assuming that it is approved at the party's conference this week, it will mark the arrest of the kind of old Labour statist producerism that the party appeared from time to time to be indulging in.

The party has recognised that after Gordon Brown's budget it cannot go on outbidding Labour on tax and spend. The Huhne document also has some coherent and serious ideas about restructuring the public services. Still hugely more comfortable with genuine social and civil libertarianism than the Tories, and more liberal than it was a year ago on economics, the Lib Dems are slowly beginning to carve out some kind of modern identity again.

That's the party. What about the man. Mr Kennedy's energy, ambition and willingness to take on elements in his own party when it is necessary have sometimes been in doubt. However, his uncontested good judgement rarely, if ever, has. On the one hand, by the time that even the ultra- optimists in his party think the breakthrough is possible, Mr Kennedy will have been around a very long time, no longer a fresh face. On the other, his appeal as a politician who doesn't speak like a politician – not least among younger, disaffected voters – is a real asset.

The good judgement matters, too. He was right to forget about Lib-Labery. And his stance on Iraq is the more interesting because during those difficult, dangerous, and result-free weeks after the bombing in Afghanistan began he resisted some of those close to him who had urged him to condemn the war. It is easier to see in hindsight that he called it right than it was then. He is right now to resist a handful of his MPs seeking now to rule out war in all circumstances, UN or no UN.

Those near him insist that Mr Kennedy now wants to go all the way, believes it is possible and has the energy to make it happen. To make the party, and in time the public, believe it too he needs to communicate that belief, without hubris, but without undue modesty, to a larger audience. His speech on Thursday needs to be a start.

d.macintyre@independent.co.uk