The media and the political class can hardly contain themselves. What’s happening in the Labour party should simply not be happening. It’s suicidal, puerile, madness, self-mutilation, narcissistic, an emotional spasm and, in the words of one Tory cabinet member, a “potential catastrophe for Britain”.

But Jeremy Corbyn’s runaway leadership campaign shows little sign of flagging. In fact, the more he’s attacked and derided, the more support he attracts. It’s an extraordinary example of how utterly unpredictable politics can be. In the aftermath of the general election, Corbyn’s name was barely mentioned as a possible candidate, as Labour’s leaders lurched to the right.

A couple of months later and the veteran leftwing MP is heading the field in polls and nominations, attracting thousands of young people to the party and packing public meetings across the country. As Corbyn himself readily concedes, it’s a political insurgency that was waiting for something to latch on to - and that something has turned out to be him.

The parallels with the anti-austerity movements that threw up Podemos in Spain, Syriza in Greece and are fuelling Bernie Sanders’ campaign for the US Democratic nomination are clear. And the claim that the influx of new members and registered supporters is fuelled by far-left “entrists” is time-warp twaddle.

He may not be able to match Podemos’s Pablo Iglesias for charisma, but he’s transparently honest and unspun

The paradox of Corbyn’s campaign is that some of the very reasons he wasn’t seen as an obvious challenger after the election are why he’s attracting such wide support now. He may not be able to match Podemos’s pony-tailed Pablo Iglesias for charisma. But he’s transparently honest and unspun, and so obviously not from the professional politician’s mould. In a political landscape full of speaking-clock triangulators, those qualities go a long way.

Not only that, but far from being the “fanatical class warrior” of the Daily Mail’s imagination, Corbyn represents Labour’s mainstream values and is making the case for a social democracy that has been driven from the mainstream for a generation.

As one young supporter at a Corbyn rally explained: “People say he is an old leftwinger or an old Marxist but to my generation his ideas seem quite new.” What she meant was simply free university tuition and the public ownership of rail and energy – common across Europe and popular with the British public.

Why are young people rallying behind Jeremy Corbyn? Guardian

Public investment in infrastructure, housing and hi-tech industry, using targeted quantitative easing, combined with redistributive taxation and rights at work: “Corbynomics” is scarcely revolutionary. As the Nobel prize-winning economist Paul Krugman put it, when Labour supporters refuse to accept a failed austerity ideology, they aren’t “moving left”, they’re “refusing to follow a party elite that has decided to move sharply to the right”.

That is what Labour’s other leadership candidates all did after the election, ditching the party’s most popular policies, such as the mansion tax and 50% top rate, in order to appease corporate business – which polling shows most voters believe Labour has in fact been too soft on. Add to that their reversion to the New Labour formulas of the 1990s and refusal to oppose George Osborne’s attacks on the working poor – and no wonder they’re struggling to cope with Corbyn-mania.

So now the mild-mannered London MP faces a wall of propaganda from almost the entire media and every Blairite has-been that can be mobilised to derail his bandwagon. Can’t his supporters understand, they rage, that someone such as Corbyn simply could never win an election, that the “rules” of politics mean elections can only be won on the centre ground? Don’t they know what happened in the early 1980s?

There’s no sensible comparison with the 1980s, when Labour was trounced after a rightwing faction broke away to form the Social Democratic party and Margaret Thatcher dined off the jingoism of the Falklands war. And the political and media establishment’s “centre ground” bears no relation to the actual centre ground of public opinion, from public ownership to taxes on the rich.

Having decided against the evidence that Labour lost the election because it was too leftwing, they now insist the party must move closer to the Tories or be consigned to irrelevance. Mass support for the anti-austerity Corbyn is definitely not part of the script. So expect the attacks to intensify – and more loaded polling and tendentious reports such as that partially published this week attempting to show the public supports austerity.

It will be hard for any Labour leader to win in 2020, given boundary changes and the fragmentation of Labour support. But is it really more likely that a New Labour machine politician can win back the party’s lost working class, Green, SNP and Ukip voters – or wow the punters with support for another illegal war – than someone at the head of a popular movement for a different kind of politics?

John Harris charts the rise of Jeremy Corbyn, finding a political world where everything is suddenly turned upside down, and where anything is possible Guardian

With the likelihood growing of a new economic downturn before the end of this parliament, while new cuts bite into the living standards of millions, the fear seems to be as much that Corbyn might succeed as that he would consign Labour to oblivion. That certainly seemed to be Tony Blair’s worry when he said the problem with Corbyn’s platform was that even if he did win “it wouldn’t be right”. And former chancellor Ken Clarke has warned fellow Tories not to underestimate Corbyn, who he believes “could win” on a left populist ticket.

Of course, Corbyn is far from home and dry. Faced with dire warnings of disaster, Labour members may still balk at the prospect. If the Islington MP does win against the odds – the result is likely to turn on second preferences – he will at least face non-cooperation in parliament and relentless hostility from the media, though the threat of immediate coups and splits may be exaggerated.

But even if he loses to Andy Burnham or Yvette Cooper, Corbyn has already succeeded in busting open a political establishment stitch-up. He has pushed an anti-austerity agenda into the heart of political debate, forced his rivals to halt their shift to the right, and brought tens of thousands of young people into active politics. Whoever wins, that movement is not going to disappear. In six weeks, the Corbyn campaign has changed the rules of the game.