The man who could be kingmaker

"Have you got any money?" Nick Clegg asks me as we stop to buy him a latte and French pastry in Marylebone High Street during a car journey to Camberley, in leafy Surrey.

Surely a sign he is in the big league, I joke; that normally happens to prime ministers and monarchs.

Clegg is the man of the hour after his starring role in the first leaders' debate a week ago. But he insists the sudden adulation hasn't changed him.

During our hour-long drive, he is repeatedly on his mobile phone, trying to book air tickets for his three sons, who have been marooned at their grandmother's in Spain for an extra week because of the volcanic ash crisis.

Clegg hasn't seen them for almost three weeks. "It's a really big wrench; I am cut up," he says.

Antonio, his eldest, is angry with him because he hasn't gone on television yet to promote his son's pet idea for dispersing the ash clouds - dropping water on them from above.

He says he doesn't read the newspapers; he doesn't want to be distracted by tittle-tattle about his past life. His exhausted aides, running on adrenalin and coffee, complain that he can't remember alleged incidents that happened years ago and which have been disinterred by hostile papers.

Press officers are now spending much of their time fending off such personality stories. Clegg shrugs his shoulders, confident there are no skeletons to find.

At the time of the first TV debate, Clegg thought all three leaders "did OK". He felt "quite nervy" at the start, but relaxed after about 15 minutes. He was surprised to be declared the winner - but not surprised at the public mood the TV debate exposed.

"It was like taking a lid off a bottle that has been shaken hard. This has been going on for a long time - the gradual disintegration of the top-down grip of the two parties. A lot of people were switched off by the choice presented to them. What happens next is very unpredictable."

He reveals the Liberal Democrats are pouring more of their still-scarce resources into both Tory and Labour-held seats not on their original 100-odd target list. "We are being ambitious without being silly about it," he says.

One problem of success is that Clegg is under even more pressure to tell us which way he would jump in a hung Parliament to which the opinion polls point. "We have to start thinking about a whole range of different outcomes that would otherwise have been unlikely," he admits.

Several polls have suggested Labour could come third in the popular vote and yet win more seats, leaving Prime Minister Gordon Brown still in Downing St after "losing" the election. "Preposterous," snaps Clegg. But true.

"If anyone wanted evidence of our clapped-out electoral system, this is it. If anyone in the Conservative Party or elsewhere still believed after such an outcome that there is no case for electoral reform, they are even more out of date with modern Britain than I thought.

"If we have a result like that, what little legitimacy left in the present electoral system would evaporate altogether. Reform would not be a matter of choice, whoever comes into government. It would be a matter of necessity so we never have such a democratic outrage again."

Contrary to speculation, it seems that Clegg would not demand Brown's departure as the price of supporting a minority Labour government - even if he had lost but won.

He makes no secret of his personal dislike of the Prime Minister - "he cannot be an agent of change" - but insists that would not influence his actions in a hung Parliament. "Gordon's record shows he is very much part of the problem, not the solution. But it is not my job to decide who every party has as their leader."

The Liberal Democrat leader knows he could have a huge dilemma in two weeks' time that could settle the future of his own party, as well as the immediate direction of the country.

There has been a long-running debate in the third party on whether it should form a progressive anti-Tory alliance with Labour - a strategy favoured by Lord Jenkins, Tony Blair and Lord Ashdown - or go it alone, in the hope of supplanting Labour as the main rival to the Tories.

Clegg makes clear he is in the latter camp, and believes that the dramatic events of the last week have made it more likely. "I really don't think the Liberal Democrats should in any way feel constrained about what we can do.

The two old parties have lost their moorings. The Liberal Party was overtaken by Labour in the 1920s. There is no rule that says that because one party is bigger than another at the moment, that cannot go into reverse."

He believes the Jenkins analysis - that the split between Labour and the Liberals made the 21st century a Tory-dominated one - may be out of date, because politics has become "uprooted" as the two class-based tribes of Labour and the Tories have broken up. "What we are seeing now is something different," he says.

The Liberal Democrat leader is equally scathing about both old parties. Dismissing Brown's call for a progressive anti-Tory alliance, he says: "There is a peculiar desperation about the Labour Party apparently planning for defeat and thinking it can save itself by talking up precisely the reform of the political system it has sought to block for over a decade."

Although senior Labour figures are encouraging anti-Tory tactical voting by Liberal Democrats in Conservative-Labour marginals, Clegg will not join such "game-playing and nods and winks ... It assumes there are fixed poles for people to choose between. The last week may have shown that something bigger is going on. People should vote with their hearts. For once there is an opportunity to go with their instincts."

Clegg's new demand for a proportional voting system - strongly opposed by the Tories - suggests a deal with Labour is more likely unless the Tories drop their strong hostility to reform.

He condemns Cameron for telling people to vote Tory to prevent Labour from clinging on to power under first-past-the-post, yet he defends this "potty" system at the same time.

"It is deeply conservative," he says.

He claims this reveals "a profound identity crisis", accusing Cameron of using "camouflage" while claiming the mantle of change.

Unlike Brown and Cameron, Clegg says he had not rehearsed for the second leadership debate this morning.

He has been so busy on the campaign trail he has not found as much time as he intended to read up on foreign affairs.

He enters it with confidence but he is not getting carried away. "I am acutely aware that what goes up can go down," he says.

- INDEPENDENT