Nick Clegg makes a final appeal to voters today to seize the "once-in-a-generation chance" for real change to Britain's unbalanced voting system by backing the Liberal Democrats on Thursday.
As polls this weekend showed that David Cameron is beginning to stretch his lead and could achieve an outright victory, after weeks of surveys pointing to a hung parliament, the Lib Dem leader insists a majority Tory government would be run by a "clique" of people with "vested interests" that are set against electoral reform.
Mr Clegg, trying to cast the final week of campaigning as a two-horse race between his party and the Tories, claims that Gordon Brown has "written himself out of the script of change" and that the Labour Party is in a fight for its very existence.
But he also twice refuses to rule out supporting a Conservative minority government if attempts to form a Lib-Con coalition fail as a result of Mr Cameron refusing to adopt electoral reform.
Yet a ComRes poll for The Independent on Sunday today puts the Lib Dems back into third place after enjoying near-equal billing with the Tories as a result of Mr Clegg's stunning television debate performances. With only four full days of campaigning to go, the Conservatives have opened up a 10-point lead over Labour, 38 per cent to 28, while the Lib Dems are on 25. The poll also suggests that the Tory strategy of warning that a hung parliament would be bad for the economy is paying off, with voters turned off the idea.
Perhaps anticipating that voters are beginning to switch back to the "old" parties of Conservative and Labour, Mr Clegg says in an interview with the IoS that this Thursday presents the only chance to deliver electoral reform. In a direct pitch to voters, he says: "Let's not let this moment slip. Let's not let this extraordinary once-in-a-generation opportunity go by. It doesn't come along that often.
"There is the chance to resettle things in a new way. It is very unusual and I just don't want people to be bamboozled or bullied or frightened by the other parties into saying they cannot take a chance on big change this time. That is the main message.
"Let us not squander this once-in-a-generation chance – because it is a once-in-a-generation chance."
Seizing on the Prime Minister's final message in the third debate last Thursday, when he said that the result on 7 May might be Mr Cameron in government, with the support of Mr Clegg, the Lib Dem leader says his Labour rival had "nothing positive" to offer voters. He says: "Brown has written himself out of the script of change in as much as the only point in having an election is to debate what changes are going to happen. His words are hollow."
The Lib Dems are now the truly progressive party as Labour fights for survival, Mr Clegg claims.
"Regardless of the outcome of the general election, there is a real existential crisis for the Labour Party. They've really got to go right back to fundamentals: what on earth is the point of the Labour Party in these changed circumstances? What kind of brand of progressive politics does Labour possess in terms of the battle of ideas?"
The Tory leader, also in an interview with the IoS, pitches to the "liberally minded" readers of this newspaper to vote Conservative, claiming only his party can introduce change by winning an overall victory. "Liberal conservative" policies on the environment and civil liberties would "die" in the messy horse-trading of a hung parliament, Mr Cameron says.
The Conservative leader effectively admits that his zeal in pushing for the TV debates, which saw his poll lead pegged back by the Lib Dem surge, was a mistake, saying his bid for No 10 had been made "more challenging". He leaves the door open to negotiation with Mr Clegg by describing the Lib Dem leader as "easy to get on with", and promises to act "reasonably and responsibly" in any hung parliament negotiations.
After admitting yesterday that he had been damaged personally by calling Rochdale grandmother Gillian Duffy a "bigoted woman", Mr Brown found that his campaign difficulties continued when a heckler rounded on him in a glass factory in Sunderland.
The Prime Minister battled on, telling supporters: "I have come here, to a region of fighters, to talk about the fight ahead. Not Labour's fight in this election – but our country's fight for recovery. Because I fight every minute of every day not for my future but the future of Britain's hard-working families. And I fight not for my job, but for you to get a better deal in your job."
Writing in this newspaper, Labour's election strategist, Lord Mandelson, warns that the Conservatives and Lib Dems together "would be a disaster for Britain". But in his interview with the IoS, Mr Clegg attempts to steer clear of what he would do in the event of a hung parliament, but he twice refuses to rule out supporting a Tory minority government. There is speculation that, in the event that no two parties can agree on a coalition deal, the Lib Dems could nevertheless support the Tories if they had the largest number of seats and votes, in the national interest.
Mr Clegg says: "I am simply not going to get boxed in about talking about anything else. It would be presumptuous; it would be arrogant."
The past 10 days have seen a hardening of position between all three party leaders. Of the prospect of a Tory Britain, he says: "You'd have superficial changes in the political system at best, a country adrift in foreign affairs, a north-south divide coming back with a vengeance. You'd have a very cliquey feeling about who's running the country ... with Osborne and Cameron and friends.
"What is this big society? It is a big society with a price tag attached. It's a bit like inviting someone to a party in a pub and find that it's your card behind the bar paying for everyone's drinks. What is emerging is what has always been there, which is a well-oiled PR machine, but basically it's disguising fake change. It's hollow. There's nothing in it. For a long time they thought they could waft into No 10 no questions asked, with a sense of entitlement to govern the country again."
Mr Clegg, who has enjoyed an extraordinary personal and political journey over the past month, rejects the suggestion that his poll surge was because of the personality-driven live debates, and denies that the Lib Dems were now slipping in the polls because people were investigating their policies. He says he has survived a "tsunami wave of bile thrown in my direction" by right-wing newspapers.
The Lib Dem leader even audaciously claims that "it is also a possibility that we might come first in the number of votes cast".
Mr Clegg once said he was an atheist, but has since insisted he is agnostic, and attempts to clear up the mystery. He says he is not a "frothing atheist" but a "questioning agnostic", adding: "It must be wonderful to have faith. My wife is religious; my children are. But it is not something that has ever visited itself on me. Maybe it will happen one day." Maybe Friday? Mr Clegg laughs. "Yes," he says.
* Mr Cameron faced further embarrassment over his party's record on gay rights last night. The Observer claimed that Conservative candidate Philippa Stroud, who is standing in Sutton and Cheam where the Lib Dems have a 2,870 majority, founded a church which believed it could "cure" gays and lesbians by using prayer to drive out their "demons".
What are voters letting themselves in for?
A clear majority – If Labour wins, it's business as usual. If it's another party, it will be invited to form a government.
No majority – Even if Labour does not have the most seats, Gordon Brown will have the constitutional right to stay until the Queen's Speech on 25 May, to thrash out coalition deal.
Tory-led coalition – Cameron could form alliance with Lib Dems in exchange for electoral reform.
Tory minority rule – If horse-trading fails, Cameron can form a minority government, making agreements on a case-by-case basis.
Labour-led coalition – Clegg can opt for coalition with Labour. This coaltion too depends on concessions.
Another election – If no government can be constructed or the administrations that emerge are too fragile, a second election could follow.
Newspapers can't vote, but this is how they would line up
Daily Express – Not declared, but supportive of the Conservatives and energetically critical of Labour.
Financial Times – As yet undeclared, but critical of Labour.
The Guardian – Liberal Democrats. "If The Guardian had a vote in the 2010 general election it would be cast enthusiastically for the Liberal Democrats."
The Independent – Not declared.
The Independent on Sunday – Anti-Tory vote for electoral reform.
Daily Mail – Not officially declared, but highly critical of Labour and, latterly, the Lib Dems.
The Mail on Sunday – Conservative.
Daily Mirror – Labour.
Daily Star – Non-aligned, but urges readers to vote.
The Sun – Conservative.
The Daily Telegraph – Undeclared, but Tory-friendly and critical of Labour.
The Times – Conservative.
The Observer – Declared last night it was backing Lib Dems.
Sunday Express – Conservative.
Sunday Mirror – Labour.
The People – Favours a coalition and urges tactical voting to prevent a Tory majority.
The Sunday Telegraph – Tory.
The Sunday Times – Tory.
The News of the World – Tory.