Teflon, otherwise known as polytetrafluoroethylene, was discovered by accident back in 1938.

Registered at the end of the Second World War, an early use was coating valves and seals holding radioactive material in the Manhattan Project, while in 1954 the wife of a French engineer urged him to use it on cooking pans.

Much later, meanwhile, the brand (as opposed to the material) came to be associated with certain politicians, those who managed to achieve that rare state of grace in which little that is negative appears to stick. Think "Teflon Tony" at the height of New Labour pomp.

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Teflon continues to coat certain politicians and their arguments to this day, sustaining popularity and credibility even in the absence of much supporting evidence.

Take austerity. As William Keegan points out in his new book, Mr Osborne's Economic Experiment, a few years ago the Conservatives went to great lengths to blame "Labour's mess" (i.e. excessive public spending) for the 2007-08 financial crash, when in fact on the eve of that crisis public spending (at around 39 per cent of GDP) was similar to that in the latter years of Kenneth Clarke's 1993-97 Chancellorship.

Blaming the crisis entirely on its predecessors in government rather than the banking crisis was, of course, a cynical political tactic, but a highly successful one; as Keegan writes, "for all the apparent political success the Chancellor and his colleagues have had in making people believe them, the charge simply does not stand up."

Mr Osborne, however, also fashioned a narrative with wider-reaching consequences, chiefly that a period of prolonged austerity was necessary in order to tidy up Labour's "mess". Even Keegan admires the Coalition's "chutzpah" in arguing that now a recovery has at last begun, then "this justifies the policies and period of austerity that preceded it".

It's a neat illustration of a how a powerful narrative and a degree of public support can sweep all before it. The annual bun fight over Government Expenditure and Revenue Scotland (GERS) also illustrates the point. On any sane reading these were bad for the SNP ("it's just basic sums," one independence supporter told me privately), yet the Scottish Government glossed over the obvious with almost comic indifference.

GERS showed what it usually shows, that even when a geographical share of oil revenue is factored in, then the amount of revenue raised in Scotland is a significantly lower figure than the total amount of expenditure. In response, the Scottish Government simply emphasised the first figure (Scots pay £400 more in tax than your average Brit) and ignored the second (they receive £1,200 more in public spending than average). Some newspaper columnists even argued that it was just a lot of numbers and didn't really matter.

At Holyrood last Thursday the First Minister grudgingly acknowledged the existence of a large gap between the two figures, but simply claimed that under independence she and her colleagues would "grow" the Scottish economy. But even accepting that rather vague alibi (most governments, after all, want to grow their countries' economies), making up the difference would require a level of growth (and within a remarkably short space of time) that would outstrip even China in a good year. It simply isn't credible.

Yet, as usual, Ms Sturgeon and her colleagues (although the Finance Secretary John Swinney appeared untypically grumpy) emerged from the annual GERS bun fight relatively unscathed. Even its modified goal of "transitioning" to full fiscal autonomy with the Barnett Formula intact (talk about having your cake and eating it) ended up looking like a reasonable position.

Again, the explanation lies in the power of narrative. During the referendum campaign Yes Scotland cleverly reframed the GERS figures in terms of percentages, thus Scots, we were told, contributed 9.6 per cent of UK taxes but "only" received 9.3 per cent of spending when, of course, the latter figure was larger in cash terms due to borrowing and other revenue. Nevertheless the narrative had it that Scotland paid in more than it got back.

Such a message was easier to project to voters than a detailed balance sheet. Layered on top of that was the general implication that Unionists were a bunch of scare-mongerers and liars, and therefore the counter-narrative, that Scotland did rather well out of the Union, often failed to resonate. So fast-forward a few months and GERS just doesn't have an impact any more. It's just a bunch of numbers.

This Teflon quality also applies to individual politicians. Those, such as the current First Minister, who are generally liked and respected by the majority of voters, are granted the benefit of the doubt even when it's quite clear they're being, as the late Alan Clark once put it, "economical with the actualité". Several watching FMQs last week were struck that Ms Sturgeon had ended up gliding over inconvenient detail in much the same way her predecessor did.

Indeed, Alex Salmond enjoys Teflon qualities of almost Blair-like proportions. Yesterday the Scottish Sun (owned by Rupert Murdoch) started serialising the former First Minister's referendum diary, which will be launched this Thursday and for which he's apparently received a six-figure advance from London-based publisher William Collins (also owned by Rupert Murdoch), although it's yet to show up in his register of interests.

Given that a) Murdoch is a controversial figure, particularly for those on the Left, and b) the Scottish Sun recently got pelters for a mock-up of the current First Minister sitting astride a wrecking ball, you might think that Salmond might attract a little flak. Not a bit of it. Confronted with evidence of him continuing to cosy up to a right-wing media mogul, Nationalists - who are usually hypercritical of Unionist foibles - fall strangely quiet.

But then Mr Salmond is a widely respected and popular elder statesman and the majority of voters, particularly Yes voters, are inclined to think well of him. Meanwhile Labour politicians, who lack such buoyant approval ratings, are subject to almost absurd levels of vitriol and outrage. Ed Miliband's kitchen becomes a general election news story, while, right now, if Jim Murphy so much as accepted £50 from the Daily Mail for a short article he'd be crucified by the same people who pretend not to notice the Salmond/Murdoch relationship.

Down in London Mayor Boris Johnson enjoys a similar Teflon quality, even when extra-marital affairs emerge and he gets trapped on a zip wire, none of it does him any harm, for Boris is Boris, and at the end of the day even non-Tory voters quite like Boris being Boris. With less entertaining, less blond, politicians, they are markedly less forgiving.

As any cook will know, Teflon coatings eventually wear off, as did Tony Blair's even before the Iraq War. Some, however, last longer than others, with far-reaching consequences for public policy and the endless adventure of governing men and women.