It is customary to wait for the patient to expire before performing the autopsy, but impatience is one of the weaknesses of modern politics, and everyone wants to know why the Tories threw away the election.  They haven't, by the way, but the events of the past week have been too far-reaching to postpone at least a preliminary reckoning. David Cameron's admirable calm since walking off stage in Manchester last Thursday and retiring to a nearby pub to drown his sorrows conceals reactions across his party that range from defeatism to murderous rage to a curious optimism.  It is going too far to talk about an existential crisis among the Conservatives if Mr Cameron does not win on May 7. Nothing is forever, including defeats. Pendulums swing. Who is to say that some sort of centre-Right government will not rule the country in a generation's time? But the long view holds no appeal for the candidates and activists currently pounding the pavements in search of votes. The Tories have a fortnight to save themselves from what most fear is an immediate, extinction level event.  The scenario they face is the one being put in place with trademark guile and ruthlessness by Gordon Brown and Peter Mandelson. The Lib Dems would trade their support in a coalition for a deal on some kind of voting reform; Vince Cable in the Treasury; and Mr Brown's head. In exchange, Labour would keep power, and Mr Brown would have the satisfaction of wiping the smile off Mr Cameron's airbrushed face for good.  At one level, there is plenty of evidence to steady Tory nerves. Across the country, canvassers report a collapse in Labour support. Voters motivated by a fierce desire to get rid of Mr Brown and his party are switching straight to the Tories. One of the untold stories of this campaign is that the Government is heading for a calamitous defeat, at least in terms of share of the vote. Labour marginals way down the scale are suddenly in reach.  Canvassers and candidates also report no evidence of voters switching to the Lib Dems as a result of Mr Clegg's performance in the first debate. There is admiration for him on the doorstep, but also a sophisticated realisation that Mr Cameron has a point: if you want to be rid of Brown, don't vote yellow. Focus groups make similar claims: Mr Clegg has impressed as a spokesman for an alienated electorate, not as a prime minister in waiting.  However, in Lib Dem marginals, and in vulnerable Tory seats, the story is different. Last week, a poll for The Daily Telegraph found a swing away from the Conservatives in the Lib Dem seats they need to win. Anecdotally, there are fears that the Tories may actually lose seats to the Liberals: Eastbourne is said to be all but lost, while Guildford and Solihull are vulnerable. Wantage, home to the arch-Cameroon Ed Vaizey, is causing concern.  But that is just the beginning: the yellow tide has seeped into the heart of Conservative campaign headquarters. Over the past week, the leadership has been running the numbers on what a Lib Dem surge might mean. It has calculated that Mr Clegg could win as many as 100 seats, and some of its most influential figures could lose theirs, first among them Oliver Letwin and Jeremy Hunt (who, ironically, has been playing the part of Mr Clegg in debate rehearsals).  At this point, the electoral maths becomes headache-inducing. Some argue that a swing to the Lib Dems on that scale would do such damage to Labour that the Tories would pick up far more seats, and could therefore do better than expected. However, the betting markets lowered expectations on the Tories again yesterday, predicting that they will get about 300 seats, making them the largest party but leaving them 26 short of an overall majority.  With the outcome uncertain, and the stakes so high, the recriminations are piling up. Steve Hilton, Mr Cameron's chief brain, is being damned left, right and centre for the lack of red meat in the Tory message and the impenetrability of the Big Society manifesto. Andy Coulson is getting the blame from those who say the fatal error was to import presidential debates into a parliamentary system. Mr Hilton voiced doubts, the story goes, but the former News of the World editor pressed on in order to placate Sky News – hosts of tonight's second debate and chief drum-beaters for the idea – and its owner Rupert Murdoch. The knives are out for George Osborne as well, not only as campaign supremo but as a proxy for Mr Cameron.  If the Tory leader is not prime minister on or soon after May 7, the parliamentary party will turn on its leader. Already the 92 Group, a club of Thatcherite MPs, is planning a meeting in the week after the election that could demand Mr Osborne's head. A coalition of the excluded, the irreconcilables, and those nursing grievances over the handling of the expenses inquiry is preparing to break its silence. Up to 20 MPs are said to be ready to speak out. With Sir Michael Spicer standing down, the chairmanship of the 1922 Committee is up for grabs. Graham Brady, the frontbencher who resigned over grammar schools, is the angry Right's choice to take over the post, instead of Nicholas Soames, a leadership favourite who would run as a unifier of both wings of the party. Mr Brady will be an effective voice for those who believe the time has come to challenge Mr Cameron's exclusive style of leadership.  To mitigate the threat, the search is on for a silver lining. Over the past 48 hours we have begun to hear lines being rehearsed. One of the shadow cabinet's most thoughtful members suggested to me that the chances of a Lib-Lab coalition winning a referendum on PR were so slim, and the scale of the difficulties facing the next government so great, that it might be worth leaving them to face the music. "Historically, Lib-Lab coalitions end in failure. We would benefit from that. Britain – and England in particular – is fundamentally Conservative, so whether in a fortnight or five or 10 years, there will be a Conservative government." Expect also to see discreet reminders of the need for discipline at a time of political flux.  There is no sign that Mr Cameron believes he could profit from a Lib-Lab regime that ends in failure. He has compelling policies, hidden by a message that is proving to be too sophisticated to explain in the time available. He is a determined politician who, to coin a phrase, is best when he is boldest, but who appears to be trying to risk-manage his way into Downing Street.  Yesterday, Kenneth Clarke gave a masterclass in why hung parliaments are bad for the country and why the economic crisis is of such severity that uncertainty would be a national calamity. This should be the exclusive Tory message from here till polling day.  For the moment, however, the only certainty is that the country wants change. Tonight, it will watch Mr Clegg knowing that he is not it. And it will wait for Mr Cameron to show why he might make a better fist of things than Mr Brown. This time, he will look straight into the camera, and hope the public finds what they are looking for. After May 6, there will be plenty of time to contemplate the whys and hows of the outcome. Now, though, the situation is perilous, changeable, and recoverable – but only just.
The nation wants change - and Cameron must show that he's the man to deliver    it, says Benedict Brogan.