David Cameron's view of a hung parliament:'It's all Cleggified Balls!'

David Cameron at last has some momentum as the campaign reaches its climax. But can he win a working majority?

(JUSTIN SUTCLIFFE)

David Cameron has met "real voters" nearly every day of the 2010 election campaign. Last week, he was confronted by Jonathan Bartley, the father of a boy with spina bifida (no Gillian Duffy moment there); later that day, he travelled to a Bolton youth centre.

But between his engagements with voters last Tuesday, he was interviewed by The Independent on Sunday in the rarefied surroundings of a private lounge at London City Airport's Jet Centre. On other days, billionaires read The Wall Street Journal there and drink espresso while their pilots refuel their executive jets. It is hot and bright and noisy on the tarmac, but in our bubble it is air conditioned and softly lit.

The Tory leader, who looks at home among the cream leather armchairs and oak panelling, is travelling by private plane to get to as many marginal seats as possible: he has an election to fight. But everyone in the room is aware of where we are. Mr Cameron's aides seem keen not to have their leader photographed with a private jet parked in the background, just outside the window.

In spite of this, he is here to make a pitch to the "liberally minded persons" who read this newspaper to vote Conservative, because, he says, his party can offer everything the Lib Dems can – "real change" on the environment and civil liberties – but have a realistic chance of achieving those things in government.

He warns "all these things could die" in the messy horse-trading of hung-parliament negotiations.

Mr Cameron, acknowledging we are in an airport, guarantees that there will be no change in Tory plans to scrap the planned third runway at Heathrow. "It is so black and white. There will be no third runway," he says.

Mr Cameron insists his party has "genuinely exciting" ideas on the environment. He lists a "green suite" of policies put together by the Tory policy guru Oliver Letwin: interactive grids, electric cars, community heating systems and decentralised planning.

Yet the "vote blue, go green" strategy of his early leadership years has faded, replaced by small government, big society, pro-marriage ideas.

There are voters who perhaps once considered backing Mr Cameron but who have been scared off by the more right-wing agenda. And the surge in Liberal Democrat support following Nick Clegg's performances in the first two televised election debates has been at the expense of the Tories.

In a renewed pitch to this part of the electorate, Mr Cameron says: "We have an argument to make to Independent on Sunday readers, as well as others, that there is a modern Conservative Party that can deliver a liberal conservatism that you want. We have to do that. We have to win those people back."

Clearly this tactic is double-edged: Mr Cameron is keeping his options open for negotiating with Mr Clegg in a hung parliament. For all the warnings from his party in the past weeks that a hung parliament would be disastrous for the economy and politics, to us he is warm about Mr Clegg's "easy manner", and promises to be "reasonable and responsible" in any negotiations. "We will play our part in providing the best possible government. It's perfectly consistent to say that and at the same time say let's not get starry-eyed about a hung parliament."

When the IoS last interviewed Mr Cameron a year ago the Tory leader admitted he had yet to "seal the deal" with the electorate.

Then, the Tories were comfortably above 40 per cent in the polls, on course for an outright victory. His favourite Scott bicycle had just been stolen from outside his house and we speculated that, just like the bike, he must have feared the election being similarly nicked from under his nose.

A year on, and Mr Clegg is threatening to do exactly that. Mr Clegg's performance in the first debate has had the most significant and lasting effect on this campaign: it has transformed Mr Cameron's chances of becoming Prime Minister from a near-certainty to only likely, possibly dependent on the breakdown of seats and tense negotiating in a hung parliament.

Mr Cameron won the third and final debate last Thursday, according to the instant polls, and this week may see him streak ahead to a position of comfort, but this weekend the polls are still pointing to a stalemate. With Gordon Brown's campaign in difficulty, it must be troubling for Conservatives that they do not have a significant poll advantage.

So, does Mr Cameron regret pushing so hard for the debates, which gave equal footing to Mr Clegg? He as good as admits it was a mistake, saying they have made his bid for No 10 "more challenging". "Don't ever let it be said that politicians don't have some principles and beliefs that they fight for," he says, the end of this sentence swallowed up by a tense laugh.

"We've done something which will be good for future elections and future engagement, but does it make it more challenging? Yeah, it sure does. It was never going to be easy. It's tough, it's much tougher than some people expected, but it doesn't mean it's not winnable. It's absolutely winnable."

Is one of his challenges in this final week to persuade voters that Mr Clegg is just another politician?

"They will come to that recognition and I think they are beginning to do that. I thought he overplayed his hand on expenses. Anyone would think it was a cross between the Archangel Gabriel and Mother Teresa we were dealing with. In the end, the choice at the election is going to come down to: who do I want to provide fresh direction and leadership for the country, rather than who scored a points victory in a debate?"

The Conservative campaign has "come under great pressure" but survived "without any wheels coming off the wagon", Mr Cameron says.

"I am very, very calm and focused about what we're doing. I don't think you can sense there's any particular stresses and strains with me."

Sitting on the cream leather armchair in the lounge, tie on but jacket off, Mr Cameron certainly does seem calm. He says he tries to get out of the "bubble" of Special Branch officers and photographers and goes home every night to spend time with his pregnant wife, Samantha, and their two children, Nancy and Elwen.

But his voice betrays tension, and he interrupts himself frequently. Whether this is from a fear of failing to secure what once seemed an easy victory or simply from being "fired up", as he says, for the final push of the campaign, is not clear. Yet how can Mr Cameron say the Conservative Party offers real change when it is opposed to electoral reform – the big undercurrent to this election?

We ask Mr Cameron about rumours that he has said, in private, that there are virtues to the single transferable vote system of electoral reform, the most proportional of all voting systems and the one that the Lib Dems would prefer. Mr Cameron says, "You can make lots of arguments [for STV] because you are able to choose between candidates of a party, so there's some choice involved."

But the problem is, he says, the constituency link is lost. Perhaps he would offer Mr Clegg a compromise – such as AV Plus, where there is proportionality and a constituency MP – but the Tory leader insists he remains opposed to electoral reform. With the three-way split in the electorate, bringing increased support for the Lib Dems, isn't the will of the people a sort of "Cleggified Cameron"? Referring to the possibility of a Labour Party led by Ed Balls, he says: "Well, they will end up with a Cleggified Balls, or a Ballsified Clegg. That is the problem we are looking at."

Ultimately, how can Mr Cameron persuade "liberally minded persons" to vote for his party when, as J K Rowling pointed out last month, the Tories keep giving them reasons not to: for example, Chris Grayling and Julian Lewis undermining gay rights?

Mr Cameron points out that the Conservatives support civil partnerships and plans to stop homophobic bullying. But he adds: "I am very honest with people. The Conservative Party had to go on a journey on gay equality; it's a journey that conservative parties the world over need to go on, and I would say we've gone a lot further and faster than others."

Yes, but a Pink News poll last weekend showed that support among the gay community for the Conservatives has fallen dramatically from 39 per cent last June to just 9 per cent today.

He concedes: "That was not a good poll ... Has it been an incident-free journey? No. Has it been fast enough? No. Is there still further to go? Yes. I couldn't be more honest about it."

Perhaps this sums up his wider campaign for No 10. After nearly five years as leader, during which he was in front in nearly every poll, the next five days may seem like the most difficult part of the journey. Can he seal the deal in time?