“Gordon could do him slowly,” a seasoned political strategist mused. “Or he could microwave him.”

That was during Labour’s sunshine week in Bournemouth that ended with double-digit poll leads and predictions of a Tory meltdown. The choice of methods available to Gordon Brown for dealing with David Cameron-seems less straightforward today.

As the Prime Minister agonises over whether to call a snap general election he is receiving conflicting advice. One faction believes the Tory leader can be “blown up” in a three-week campaign; another is urging a slow, relentless unpicking of the Cameron project.

His calculations are further complicated by internal debates over how the public will react to a worsening economy and how low a Commons majority could credibly be framed as victory.

The Conservatives’ conference began according to the “disaster movie” script. “We have had a fantastic year,” Simon Mort, the conference chairman, said on Sunday, before being barracked by delegates unable to hear because of a failure in the sound system. On the football pitch things weren’t going any better. “We don’t seem to be doing very well,” Samantha Cameron observed as she watched Tory MPs lose 10-0 to a team of lobby journalists.

Then came George Osborne’s “million-pound moment”. If Mr Brown calls an election and fails to win it convincingly, then Monday’s speech by the Shadow Chancellor will be seen as the moment that the political narrative took an unexpected turn.

Raising the threshold for inheritance tax to £1 million is one of Mr Cameron’s main offers to the electorate. It is a proposal that had been scrutinised by intense private polling throughout the summer and been the subject of a fierce internal debate among the party leadership.

In the event Mr Osborne – backed by evidence from focus groups – won the argument against those who said that such a middle-class giveaway would, by increasing relative inequality, undermine the modernising message. The whoops of delight in the Blackpool Winter Gardens and the subsequent poll bounce have vindicated his view that slashing the numbers exposed to death duties could be an election winner.

Over in No 10, however, the proposal came as no surprise. There, six key advisers have for a number of weeks been holding what one calls a “rolling conversation” on whether to hold an election. The six are Ed Balls, Mr Brown’s closest ally and now Schools Secretary, Ed Miliband, the manifesto author, Douglas Alexander, the election co-ordinator, Spencer Livermore, director of political strategy, Fiona Gordon, political secretary, and Peter Watt, Labour’s general secretary. In meetings, by e-mail and via mobile phone conferences this core group has been talking about an autumn poll incessantly – and most of its members have become convinced over the past month that Mr Brown should go for it. Mr Osborne’s offer on inheritance tax, his pledge to scrap stamp duty for first-time buyers, and the effect both would have on polls in the short term, had been anticipated by this group, according to an influential figure. “We expected to be either a couple of points ahead or neck and neck at this point,” the insider said.

Confident that Labour can unpick what it cannot match on tax, those urging an early election are also persuaded by data from Deborah Mattinson, Mr Brown’s pollster, showing that few voters see Mr Cameron as a potential Prime Minister. “Middle-aged women looking at him just don’t see him handling Britain in a crisis. When they are asked to choose they won’t choose Cameron.” The Tory leader could be “microwaved” in a short, sharp campaign, this group believes.

Although the Tory share of the vote swings dramatically, Labour’s figures have been steady. Should they hold up through an election campaign, even the staunchest Conservative could not expect Labour’s majority to fall much beneath 35. Although that is fewer than the current 69, the pro-camp believes a majority of around 40 could easily be framed as a victory.

More cautious advice has been supplied by a group of more experienced Cabinet ministers, including Alistair Darling, the Chancellor, Jack Straw, the Justice Secretary, and Geoff Hoon, the Chief Whip. They suggest that it will be difficult to counter comprehensively the popularity of the Tory tax offers in a short campaign. They point to the volatility of the polls and that a contest would be fought against a gloomy backdrop, including the possibility of a foot-and-mouth epidemic.

For this group Mr Cameron is best slow-cooked. If they win the battle it is certain that the PreBudget Report will include voluminous information – on the number and wealth of nondomiciled residents, for example – to help to unravel Mr Osborne’s calculations.

Those urging the long game would have taken heart from Mark Penn, chief strategist to Hillary Clinton and a former adviser to Tony Blair, who urged caution when he addressed a think-tank on Thursday night. It was better to campaign on record than promises, Mr Penn told the Policy Exchange. But Mr Brown is inhibited by his need to dissociate himself from Mr Blair, continued Mr Penn. Better, therefore, to use the next two to three years to build a record of his own to present to the electorate.

It would be a mistake to present either camp as homogeneous; some advisers and ministers shuttle between the two. The position of Mr Darling is most difficult of all to read. The Chancellor told The Financial Times yesterday that Britain could expect an economic slowdown next year, but whether this means he is in favour of an early election is unknown. Alan Greenspan, the former chairman of the US central bank and an adviser to Mr Brown – he visited the Prime Minister on Monday – has been no less downbeat in public.

It is likely that Mr Brown had Mr Greenspan’s predictions of economic woe – as well as the enthusiastic response to the Tories’ promised tax cuts – ringing in his ears when he left London for Baghdad earlier this week. For 36 hours during his flying visit to Iraq the unofficial election committee heard nothing from their leader, and it seems there was a wobble of confidence. Was he preparing to call the whole thing off?

Insiders are convinced that the Tories got wind of this dip in confidence and this led them to up the ante. When Mr Osborne spoke to The Times on Tuesday he was on bullish form. “He’s left us in this position where either we have had more advanced notice of when a general election is going to be than almost any Opposition has had in recent times, or he bottles it,” he said.

Senior Tories say they were struck by how late and ineffective was Labour’s counter-attack. They struck home on Wednesday with a second blow, accusing Mr Brown of using British soldiers as window-dressing when he announced a further reduction of troop numbers in Iraq.

On Wednesday morning Mr Cameron’s aides went to collect him for an engagement ahead of his key speech. To their horror they found his room empty. The Tory leader and his wife had slipped from the back entrance of the Imperial Hotel for a walk along Blackpool beach. Mr Cameron had wanted to clear his head before delivering a speech without notes whose spontaneity had been meticulously practised.

At its climax he called on Mr Brown to go to the country. “Why don’t you go ahead and call that election?” he demanded to thunderous applause.

It is claimed in Downing Street that Mr Osborne and Mr Cameron made a fatal miscalculation in believing that the election was off. There was a debate about how hard to counter the Tory attacks, they claim, but it was decided that “muddying the water” would look tacky.

Mr Brown – emerging from a meeting with Paul Kagame, the Rwandan President, on Wednesday afternoon – engaged again with his election advisers and gave them little reason to believe that he was about to “bottle it”. Mr Brown made clear he was itching to fight back and was particularly enraged at accusations that he had used the Iraq visit as a cynical stunt.

Preparations for an autumn election – first revealed by The Times in August – continued apace yesterday as the finishing touches were applied to Labour’s manifesto.

Tomorrow Mr Brown will have completed his analysis of data from a poll of 150 marginal seats which shows that the inheritance tax offer has had a big effect on the Tory share of the vote. The evidence – presented by Ms Mattinson and Stan Greenberg yesterday – is leading both pollsters to recast their advice in more cautious terms.

He must decide how certain he can be that he can sow enough doubts about Mr Cameron and his sums before early November to be sure of victory. Asked last night what the latest prospects of an early election were, one of his closest aides said simply: “Heads or tails.” In fact, Mr Brown must use his gut. With both evidence and advisers so evenly divided he can trust nothing else.

An early election?

FOR
Economic outlook may worsen next year
Polls show Cameron is not seen as potential Prime Minister
Allows Tories less time to out-spend Labour in marginal seats
Tory bounce is already showing signs of dipping

AGAINST
Hard to counter Tory tax plans in short campaign
Polls since summer have been volatile
Rising jail numbers may force thousands of prisoners to be freed early
Dark evenings may hinder canvassing and depress turnout
A smaller Commons majority for Labour would weaken Brown

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