Hung parliament? The question no-one is prepared to answer

Yet the opinion polls all point to another hung Parliament – where no one party has an overall majority with more than 50 per cent of the seats in the House of Commons.

The simplest solution would be to just run the General Election again, as happened in 1974, with Ed Miliband seeking a majority and the Tories trying to keep David Cameron as leader long enough to have another go.

It is easier said than done.

Indeed the law passed in order to create the "strong and stable" coalition government of Conservatives and Liberal Democrats could well have serious implications for Ed Miliband if he crawls across the finish line to Number 10.

Before 2010, it was in the gift of the Prime Minister to decide when to go to the country, as long as it happened within five years of the previous election.

Gordon Brown had the chance to call a snap election in 2007 after he took over from Tony Blair. He chose not to. And it cost him dearly.

If Ed Miliband does not win a majority, but manages to cobble together an alliance with the SNP, he might well want to take a leaf out of Harold Wilson's book in 1974.

That year the Tory Prime Minister Edward Heath had called an election in February on the basis of "who governs Britain?"

He had wanted to take on the trade unions. The answer he got was "we're not really sure". Labour became the largest party, but did not have a majority.

An attempt by Heath to join forces with the Liberals failed. Wilson became Prime Minister but he was 17 seats short of a majority.

In October of that year he called another election.

It was dull and inflation was still running high. But Labour was at least able to say it had managed to end the miners' strike.

As a result, it was rewarded with another 20 seats and a slender majority of three.

Heath had stayed on as Tory leader for the second election. The following February he was replaced by Margaret Thatcher and the rest, as they say, is history.

So what would happen to David Cameron if, as is entirely possible, he loses seats but Labour does not win a majority?

It is something no-one in the Conservative party is prepared to discuss on the record.

But they would be foolish to not even consider the prospect of a Plan B.

The Prime Minister polls better than his party. That means there are people who don't like the Conservatives but do prefer him to Ed Miliband.

In the scenario where the Tories are down but not out, it has been speculated that a "praetorian guard" will form around the Prime Minister.

MPs will be urged to get the message out through the media that they still back him as it is likely that members of the backbench 1922 Committee will begin moves to replace him as leader.

Cameron loyalists would have to move quickly to save him.

The pressure will come from all sides for the Prime Minister to resign if Ed Miliband wins the election.

He will not want the humiliation that Brown suffered during the days of horse trading in 2010 before the coalition was formed and he was accused of "squatting" in Downing Street.

One Tory MP was reported to have said: "There is an attempt to form a praetorian guard round David. We are being asked to speak up for continuity and to say that our best option is to keep our leader. It is a move to counter the malcontents.

"It would be extremely foolish to replace David. He outpolls our party. The right just obsess about their issues and never look to the bigger picture."

The Prime Minister has not helped things by going spectacularly "off message" and revealing he does not want to serve a third term.

Speaking during a visit to the West Midlands this month, he said he wanted to live in Downing Street for the "next five years".

But there is still the prospect his party will want him gone mid term so a successor, possibly Boris Johnson, could have time to bed in.

The praetorian guard theory would work if another election is coming in October.

Ed Miliband is refusing the entertain the idea. Speaking during a visit to the Midlands, he said: "I'm only interested in having one election – one that produces a Labour government."

If he does do a deal with the Nicola Sturgeon, Alex Salmond and the Scottish Nationalists – and he promises there would be no coalition with them – he could find himself coming under increasing criticism from English voters for concessions he might make to Edinburgh.

Five years of government would seem a very long and arduous task with such an uncomfortable set of bedfellows

There is unlikely to be the choice though.

The Fixed Term Parliament Act, introduced by the Coalition, sets the date of the General Election at exactly five years since the last.

There are only two ways that can be changed without repealing the rules.

The first is if the House of Commons resolves "that this House has no confidence in Her Majesty's Government". That triggers the General Election unless another vote restores confidence within 14 days.

The other possibility is by a vote. But it has to be by a two thirds majority. That means large numbers of the opposition have to agree too. And it wipes out any element of surprise the incumbent government may have by springing a planned, secret "snap" election.

The chances are that, whichever government is formed in the days after the election, we will have until 2020.

And if that means bitter rivals have to put aside their differences and co-operate in a marriage of convenience, then we are all along for the ride . . . for better or worse.