Jeremy Corbyn is the new leader of the Labour party. He was elected in the first round of the STV-style race by a thumping margin over his three rivals, each of them a New Labour type of some flavour or another, none of whom ever really threatened his lead. At the outset of the campaign he was seen as a “token leftie”, his candidacy a matter of lip service to the party’s left-wing, just as Diane Abbott’s candidacy in 2010 had been. As his lead in the race became clear, Corbyn found himself denounced both within and without the party as a loony leftie, a communist, a friend of terrorists, a throwback, a threat to national security and plenty else besides. Labour’s membership, perhaps convinced of the need for major change by their surprise defeat in the general election, elected him anyway, handing him the greatest mandate a leader of a British political party has ever enjoyed.

The preferred buzzword of Corbyn’s detractors now is a simple, one-word argument; “unelectable”. From New Labourites watching “their” party dance from their grasp, to Tories perturbed by a leftward shift in the political landscape, via a news media largely sympathetic to right-wing framing, the word on Corbyn is that he cannot win an election (apart, presumably, from the one he just won). To the New Labour faithful, Corbyn’s presumed unelectability is a matter of bitter despair, which may yet play out in splits or defections. To the Conservatives and the media, “unelectable” is a word spoken half in jeering mockery and half in self-reassurance.

I’d like to dissect that word and its meaning a little. The implication is that Labour’s supporters (almost a quarter of a million of whom voted for Corbyn) are entirely out of touch with the nation and have elected a leader who will only serve to further alienate the broader electorate. This assumes that the British electorate as a whole is on the political right of Corbyn, are closer ideologically to the Tories’ position, and will therefore reject Labour outright at the next election in 2020. This assumption is based on the Downs model of political decision-making; there are some problems with applying that to the UK which I’ll go into momentarily, but first I’d like to address the elephant in the room.

The elephant in question is this; those arguing that Corbyn is “unelectable” today were incapable of predicting the outcome of this year’s general election only hours before it was held. Political opinion polling in the UK is in a state of unimaginable crisis. Its methodologies are broken and the data it produces is junk. This does not mean that in the absence of data we may assume the preferences of the British people to be whatever we feel like; but it does mean that anyone throwing around terms like “unelectable” is uninformed at best, and at worst, an outright charlatan. If predictions of electability in the UK actually held even as much water as a sieve, Ed Miliband would be Prime Minister and you’d never even have heard of Jeremy Corbyn. Perhaps, in time, opinion polling in the UK may elevate itself back to a position of trust, but for now, organisations haughtily proclaiming the likely outcomes of Corbyn’s leadership (or anything else, for that matter) based upon hastily-conducted polls are to be treated with no more respect or gravity than tin-pot prophets, mystic oracles, and grannies with a knack for interpreting tea-leaves.

Coming back to the Downs model, then; the reason some people think Corbyn is unelectable is because the Downs model predicts that in a two-party system, both parties will veer towards a centrist position and their policies will become increasingly similar. This is based on an assumption that two-party systems emerge in nations where the electorate’s political preferences fall roughly on a bell-curve, so that the country is broadly politically homogenous and there’s a big swell of voters in the centre of the graph, for whose votes both parties compete. Supporters of this model would point to New Labour’s abandonment of various Old Labour principles (e.g. Clause IV, its commitment to socialism) and the Conservatives’ move away from core tenets of social conservatism (e.g. dropping support for the homophobic Section 28 and instead supporting equal marriage) as evidence for this process in the United Kingdom.

The Downs model, however, is a massive simplification – Downs himself acknowledged that the two-party system he described was an ideal, and that it would never be stable in a country which was not extremely homogenous in political preferences. That’s clearly the case in the UK; the share of the vote enjoyed by the two main parties has fallen steadily in recent decades, and parties such as the Greens, UKIP and the Liberal Democrats (though the latter has been laid low, at least temporarily, by their unpopular participation in coalition government) have seen their vote share rise, even if gains of actual seats have been held back by the archaic First Past the Post electoral system. Turnout in general elections is also fairly disappointing; a third of registered voters don’t bother to cast a vote, implying either apathy or a sense of being poorly represented by the candidates on offer, or most likely, a bit of both. The overall picture is of precisely the lack of homogeneity that Downs predicted would cause instability in the two-party model; so boldly basing the claim of Corbyn’s unelectability upon an assumption of a stable two-party system is foolish at best.

Besides; are we truly expected to accept that Jeremy Corbyn’s economic ideas, which are broadly centre-left and would not raise eyebrows in any developed social democracy, are a radical departure from the British political norm, while simultaneously accepting that the present Conservative government’s policies are just business as usual? Those policies include the privatisation of the National Health Service and of major parts of the police, military and education systems, relentless attacks on disability benefit and in-work benefits for low income earners, and the marketisation of third-level education such that higher-ranked universities may charge significantly higher fees to students, none of which seem remotely in line with the post-war political consensus of the UK. Shorn of the millstone around their necks that the Liberal Democrats became in the last parliament, the Conservatives have lurched sharply to the right. In fact, based on a comparison to the centreline of British economic policy in the post-war era, Corbyn’s policies are no more radical, “loopy”, or “crazy” than those currently pursued by the Conservatives; if anything, they are more centrist.

So Labour goes left; the Conservatives go right. One might equally shout “unelectable” at either one of those parties, for all the valid data we have to go upon. In truth, though, the question of electability is neither here nor there, because there isn’t going to be an election until 2020. Rather, the question that’s playing across the minds of more tactical thinkers in Westminster, I suspect, has everything to do with another political concept – the Overton Window. This is a political communications theory which essentially says that the general public, as a consequence of public and media discourse, develops a “window of acceptabilty”; any idea or policy which falls outside this window is crazy, insane and dangerous. Crucially, this window moves; people change their minds, often surprisingly rapidly. Supporting equal marriage in the USA would have been outside the Overton Window a decade ago; today it’s firmly in the middle. That doesn’t mean everyone agrees with it, but nobody in the mainstream of politics will brand you a radical, insane threat to the nation for supporting it any more.

The triumph of the Tories since the financial crisis of 2008 has been in hauling the Overton Window of UK politics firmly to the right. Both Labour and the Liberal Democrats have been complicit in this; both parties essentially supported, or did not challenge, Conservative narratives about overspending prior to 2008 being somehow responsible for the financial crisis, about immigration being a “problem”, about people on benefits being “scroungers” (an amazingly successful and utterly depressing neo-liberal coinage), and so on. Even with the somewhat left-liberal Ed Miliband in charge, Labour seemed to think that its best chance at returning to government was to align itself broadly with Conservative policy. This caused two problems; firstly, as George Monbiot would have it, many voters seemingly reasoned “why vote for the echo when you can vote for the shout?”; secondly, it meant there was no pressure on the Overton Window, which rapidly slid rightwards, supported by the majority of the British news media, which is largely owned and controlled by offshore billionaires with a clear vested interest in right-wing economic policy.

For Corbyn to bring Labour left as the Tories continue to swing right creates, for the first time this millenium, a genuine battle over the direction of the Overton Window. The only way to move that window, after all, is to get out and pull; only by proposing, supporting and defending policies in the “loony” space at the edges do you haul the window of political acceptability into your court. Corbyn won’t face election for nearly five years; he has at least three years to drag Britain’s perception of what is acceptable, sane policy back onto ground that is more comfortable for Labour. In the process he will, I hope, ignite genuine debate and give the electorate some sense that there is a genuine choice emerging in British politics. Where we go from there is anyone’s guess; but until we see the results of that process (which will be messy, and bloody, and will get very, very nasty along the way), anything we say about 2020 really is nothing more than a guess. “Unelectable”? Come back and talk about that when there’s an actual election on the way. Until then, Corbyn’s job isn’t to win an election; it’s to change the landscape of British politics so that future elections have any hope of being won from the left again.