For well over two years the pundits, pollsters, psephologists and their fellow necromancers have been trying to figure out the secret of Kevin Rudd’s amazingly consistent popularity. How could a man who was so, well, ordinary scale such extraordinary heights of approval?

But while the pundits disputed, one letter writer to the Sydney Morning Herald had no doubts. The answer lay in the single word “Integrity”. While most politicians saw it as an obscure and irrelevant philosophical concept, Rudd actually took it seriously — indeed, he lived by it.

It was, and is, an wonderful political asset; but those who live by integrity can also die by it. And it is this that makes the so-called Utegate furore so dangerous for the Prime Minister and his government.

On the face of it, we are talking pretty trivial stuff, as the punters appear to realise. In Monday’s Brisbane Courier-Mail, hardly a Labor lovers’ journal, four out of the five letters on the subject berated the opposition for carrying on about the loan of a rusty truck when the country was teetering on the edge of recession. But this unfortunately for Rudd and his treasurer Wayne Swan, is to miss the point.

The real issue is not whether Rudd accepted a gift from a friend and neighbour, car dealer John Grant who also happened to be a petitioner, or even whether Rudd helped the donor to access government largesse. It is, quite simply, whether Rudd has told the unvarnished truth about the episode. At the time of writing, this would seem to hinge on whether the alleged email from Rudd’s office to Treasury which Senator Eric Abetz quoted last week actually exists, and if so whether it is genuine. If it does and it is, Rudd is in very deep trouble.

Misleading the parliament over such a matter is, for the traditionalists, a hanging offence. In recent years the penalty has seldom been enforced; John Howard got away with a blatant porky at least once (when he denied having a meeting with Manildra boss Dick Honan) and undoubtedly standards have slipped over the last decade or more. But it should be remembered that Gough Whitlam sacked two senior ministers, Jim Cairns and Rex Connor not because of incompetence or private or public laxity but simply for misleading parliament; and by doing so he ultimately brought down his own government. This is the level of integrity to which Rudd aspires.

Fortunately for him, by the start of the week (when this is being written) the case against him was looking very shaky. For some time Malcolm Turnbull has been flogging the story of a smoking gun — the alleged email from Rudd’s office to Treasury — to anyone who would listen, and he actually stood over Andrew Charlton, the staffer who allegedly sent it, demanding that he confess or face fearsome consequences. But Turnbull has not produced the email; nor has Abetz and nor have any of the Murdoch papers which have been gleefully carrying its alleged contents.

The only hard evidence for its existence has come from a Treasury official by the marvellously Dickensian name of Godwin Grech, and he has changed his story at least once, admits he may have got it wrong and has been presented, by the Motor Traders Association, with a plausible excuse for a mistaken recollection. Unless the auditor general or the federal police, both of whom have been put on the case by Ruff himself, come up with evidence which exhaustive searches within the public service have missed, Rudd would appear to be home free. And since the case against Swan — that he corruptly gave Grant preferential treatment — only makes sense if he was doing so at Rudd’s behest, the government as a whole is pretty much off the hook.

Some of the mud will probably stick; Rudd’s snow white image has undoubtedly been tarnished, which probably explains why he is so angry about it. But Turnbull will suffer most. Running with a hoax email need not be a capital crime, unless, of course, he knew it was a hoax or, worse still, was complicit in concocting it. But he still looks like a goose and an obstinate and malicious one at that. Turnbull’s political strength has always been his supposed intellectual prowess; if he turns out to be just another mug politician it will be an almighty fall, especially if it comes through the agency of a hapless invalid named Godwin Grech.

Turnbull will be seen, for a while at least, as a figure of fun, and, for a while at least, Peter Costello is still in parliament. Could he still be prevailed upon to make one last effort for the party for which, he says, he has sacrificed so much over the years and finally take the reins? The alternative, it is now clear, is to be remembered not, as Tony Abbott gallantly avers, the best Prime Minister we never had — he never even tried, so how could you tell — but as a sort of appendage to John Howard, useful and comfortable for a time, but, in the end, dispensable, like a piles cushion.

Costello’s pride just might drive him to change his mind yet again, but if he did drag himself to the starting line it would involve breaking the habit of a lifetime. As early as 1997 the older and wiser heads in the press gallery picked him as too lazy and gutless. By 2007 all but his keenest barrackers had got tired of playing Waiting for Godot. Perhaps his political epitaph, like his political life, should come from that play, where one of the endlessly waiting tramps philosophises: “Let us not speak ill of the dead. Let us not speak well of them either. Let us not speak of them at all.”

Fly away, Peter.