SAVVY political analysts often refer to “the Overton Window” these days.

Like many ideas that first sprung up in the United States, this once-obscure poli-sci buzzword has floated across the Atlantic – like triangulation and third-way politics – and is now routinely tossed about by talking heads to explain everything from the rise and appeal of Donald Trump to why Britain voted to leave the European Union.

Politico described it as the “go-to nerd phrase” of the current political era.

And not wanting to seem gauche, Britain’s ­professional politics-understanders have enthusiastically incorporated the idea into their patter, such that the average TV ­talking head doesn’t even feel the need to define their terms anymore.

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It’s become one of those shibboleths that demonstrate you’re a political insider – ­savvily explaining how savvy politics works to unsavvy saps like you and me on behalf of the sensible centre, and whatever ­punishing and unpleasant political idea has been decreed sensible, reasonable and ­moderate this morning.

But something curious happened in the transplantation of this idea from American to British politics.

A concept which began its intellectual life as part of a radical’s toolkit for thinking about how to shift public ­opinion towards what were one perceived as extreme positions has become the ­latest pseudo-intellectual justification for the cowardice and capitulation of the Labour leadership on everything from taxation to immigration, asylum and crime, defence and the role of business in the NHS.

It’s become a pompous way of living with the cramped moral parameters of what Britain’s ideological reactionary and often astonishingly unrepresentative media is prepared to countenance.

Like much else in British politics, it is saturated in ­cynicism masquerading as right-thinking, lack of ­ambition redecorated as sensible politics, and used to justify the ­proposition that nothing can, should or must change, ­whoever happens to be in control of ­Downing Street.

In essence, the Overton Window means “the acceptable parameters of public ­opinion at any place and time”. Which ­political ­ideas are regarded as ­common sense? Which proposals get dubbed “controversial” and which pass as ­“sensible” changes?

Which ideas are represented as the preserve of cranks and oddballs, impractical, unreasonable, and even ridiculous, and which ridiculous ideas pass to popular acclaim? And who decides what the boundaries of thinkable ought to be?

These boundaries aren’t given and they aren’t static. Some changes seem to ­happen almost organically. Social and ­political change has an unpredictable logic of its own, nudged this way and that by generational shifts, crystallising events, economic circumstances and educational campaigns.

You don’t need to think too far in our history for some powerful examples of dramatic reversals in public opinion ­shifting the mainstream.

Sometimes, some political systems will be prepared to countenance a ­broader range of political ideas as part of ­political debate.

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This can be one ­effect of ­proportional representation – in a rainbow parliament; allowing a greater diversity of voices their space in public debate. But in other times and places, a far narrower variety of political ­aspirations will be tolerated.

British politics largely ­operates on this second model – with the ­reactionary ­establishment and the feral media ­spending much of its time policing the ­legitimate scope for ­adopting positions it decrees are “radical” and ­“extreme”, while simultaneously ­incubating ­outlying, outside and increasingly extravagant opinions from the edges of political ­acceptability, laundering more and more right-wing talking points into what they’ve decided ought to be legitimate and ­acceptable.

This reflects the activist origins of the Overton Window.

When you dig into it, the concept has an interesting genealogy. First coined by the American political lobbyist Joseph Overton in the 1990s – and worked up by his colleague Joseph Lehman after his untimely death in 2003 – the Overton Window didn’t spring out of an obscure doctoral thesis or professorial lecture but as a nifty slogan in support of right-wing ideological pan-handling.

The metaphor seems to have begun life as a marketing gimmick aimed at ­persuading reactionary American funders to invest flipping great wadges of cash into the kind of free-market think tanks Overton worked for.

Overton was trying to persuade these deep-pocketed men and women that investing their cash in his free-market ideas was good coin – but had to overcome a degree of resistance about what practical utility this investment in ideas would generate.

Take a few examples from our own time. If your mission is to increase ­social acceptance for privatised healthcare in the UK, how would you go about it?

If you wanted to give the executive more and more legally unchecked power, how would you persuade public opinion this is a good idea? How would you go about ­discrediting then dismantling the ­external systems holding them to account?

Overton’s key message was that ­ideological outsiders need to be ­persistent. Put your controversial ­political ideas ­consistently on the table – keep banging on about them, mainstream the argument, recruit media and political allies to take up your cause – and eventually, your outsider notions once shared by three men and their dog might just shove out the normative competition, enter the political mainstream and ­become ­government ­policy.

Today’s heresy ­becomes ­tomorrow’s ­orthodoxy. Today’s unthinkable proposal might be ­tomorrow’s common sense.

I doubt Mahatma Gandhi was a ­major inspiration to Overton and his free-market colleagues in the Mackinac Center, but this formulation has strong echoes of the four stages identified in the famous quote: “First they ignore you, then they laugh at you, then they attack you, then you win.”

The 2016 vote to leave the European Union is a powerful example of the kind of persistence Overton may have had in mind. Euroscepticism planted itself deep – not just in the Conservative Party but across countless House of Commons speeches and parliamentary questions, newspaper editorials and misinformation over decades and decades and decades.

Structurally, advocacy for Scottish independence has a similar character, ignored, then regarded as crackers, then aggressively confronted – but we’re still stuck at stage three.

One striking feature of this analysis is the peripheral role it allocates to politicians in shaping public opinion.

As Lehman later argued: “Public officials cannot enact any policy they please like they’re ordering dessert from a menu. They have to choose from among ­policies that are politically acceptable at the time.”

Rather than being in the business of shifting the Overton Window, he argues: “Lawmakers are actually in the business of detecting where the Window is, and then moving to be in accordance with it.”

On this conception, the effective politician is the one best able to locate the invisible edges of this Window of public opinion and shape their political pitch accordingly. But the critical question here is – acceptable to whom, exactly?

It’s difficult to avoid the conclusion that “public opinion” no longer means “things the public actually believe”. ­

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Because in British politics, several ­mainstream ­ideas held by substantial majorities of the ­public are routinely dismissed as ­laughable, ­unthinkable and ridiculous by our political leaders – from ­nationalisation of key resources, to increased levies on the super-wealthy, to widespread and well-founded dismay of the hurricane of violence which has been unleashed on Gaza.

These days, the Overton Window is still sometimes used as a way of ­explaining ­social and political change – but more often than not, it’s used by supposedly “reasonable” political insiders to give the illusion of intellectual weight to ­craven politicians sticking like glue to the ­dysfunctional status quo, and explaining why nothing important can be allowed to change.