Around once a year now, something bubbles to the surface that shows how broken mainstream politics has become. Sometimes these things endure; often they fizzle out. But from the brief season of Cleggmania, through the on-off rise of Ukip and the so-called “green surge”, to the great political reformation in Scotland, Britain is experiencing its own version of the tumult that has broken out all over Europe. A politics built around fortysomething career politicians and three parties that fixate on an illusory centre ground is in increasing trouble. Even if the Conservatives have enough support and strength of purpose to ride all this out (for now), the Labour establishment is being buffeted by winds that seem to grow more ferocious by the month.

Jeremy Corbyn's Labour leadership bid has a momentum even he didn't expect Read more

Jeremy Corbyn was in Luton on Tuesday night, doing his thing at a leisure centre in front of an amazingly diverse crowd of around 400 people. I was there to make a film for the Guardian – and as soon as I arrived, a pretty obvious comparison sprang to mind. It felt like Scotland a year ago, when people congregated in the same kind of numbers, drawn by a vivid alternative to the politics of cuts and cruelty, and voices that might not talk in cliches – “hard-working families” and all that – but described the world as it actually is.

Corbyn delivered – in his own rambling way. The reward was two standing ovations and another reminder that, as things stand, he seems increasingly likely to pull off the miraculous feat of winning. Following the YouGov poll last week that put him 17 points in front of his nearest rival, a private survey reported on Tuesday by the Daily Mirror had him twenty points ahead; my phone is now buzzing a couple of times a day with awed texts from Labour people who realise he might actually do it.

There is a poetic justice about this. As Corbyn rises, Andy Burnham is suddenly styling himself as the faux-radical saviour of a party “scared of its own shadow”. But do not forget how the latter’s campaign for the Labour leadership began: with a speech at the City offices of a corporation associated with huge tax avoidance, which parroted grim lines about how businesses such as these deserved “wholehearted support”, quickly followed by a claim that when talking about benefits, Labour had to be careful not to speak for people who want “something for nothing”.

Yvette Cooper is now at pains to present herself as the very embodiment of feminism and greenery but spent May and June apparently trying to say as little of note as possible, while exhibiting that awful modern Labour tendency to boil even the great causes of the age down to borderline inanity and talk to people as if they are stupid. (Witness a campaign questionnaire that demands its recipients must tick one of five boxes, from “strongly disagree” to “strongly agree” next to such imperatives as “end child poverty in a generation”.) Liz Kendall’s progress, meanwhile, underlines a truth as banal as some of her rhetoric: that if you stand before a body of people and suggest that a great deal of their most fundamental beliefs will have to be thrown overboard, they may not like you very much.

Ergo Corbyn, and the fascinating phenomenon of a profoundly ideological politician making hay thanks to the volatility of post-ideological politics. In Luton I spoke to one or two people who shared his old-school convictions. But the single biggest share of people there – among them, a large number who were under 30 – were more open, curious and drawn by much more human factors. What mattered to them, it seemed, was not how much Corbyn may have taken from Karl Marx but qualities that have as much to do with tone as content, and clearly set him apart from his rivals: clarity, moral oomph and an evident sense of purpose.

(There was a time when Labour’s big figures could combine an emphasis on the pragmatics of power with precisely those things: between 1994 and 1997, Tony Blair was a particularly dab hand. But something about the current Labour generation suggests that knack has been lost and left the vacuum into which Corbyn has happily stepped.)

Corbyn-mania and the Labour party’s record under Tony Blair | Letters Read more

In some ways, though, he is more like his fellow contenders than his supporters would like to admit. He apparently has nothing to say about the huge social and economic factors that underlie Labour’s decline as an electoral force, suggesting instead that the solutions to its travails lie with the magic bullet of being “anti-austerity”, this or that policy, and the old foundations of its support – the unions, chiefly – being magically revived. There is something unavoidably depressing about the fact that the supposed radical in the contest apparently has nothing to say about changing the voting system. Beyond a vague insistence that Labour has to somehow turn itself into a “social movement” he does not talk about working with other parties, nor how a force as damaged and discredited as Labour could bond with other groups. Frequently, in fact, one gets the sense that his aim is to simply pull the same old levers – but in a leftwing way.

There again, I am less interested in him than what his candidacy, in tandem with Labour’s new voting system, has let loose. Every anti-Corbyn intervention has only seemed to boost his support. As much as anything, the daily cacophony of pro-Corbyn noise on Twitter and all those packed meetings symbolise something beautifully simple: people refusing to do what they’re told, which is surely the stuff of democracy at its most raw and thrilling. The choice, as many see it, is not between imminent electoral salvation and oblivion but two rather more complex outcomes: the election of another empty politician who will enact their own version of the Ed Miliband tragedy or the hope that Labour might reassert its essential values, and begin finding out what exactly 21st-century leftwing politics might actually entail – with the participation of people like those who congregated in Luton at the heart of what happens. Would anyone seriously deny that the renaissance of meaningful Labour politics is going to take a long time? In that sense, the cleverer Corbynites know they’re taking a risk but given the parlous state of the party and the long road back to relevance, it is perhaps not quite as big a risk as some people would like to think.

Every anti-Corbyn intervention has only seemed to boost his support

To some people, that will sound uncomfortably glib: redolent, perhaps, of the kind of leftwing politics that tends to games and calculations, and forgets the real world.

In me and many people I know, it triggers an ambivalence that would probably take another 15 articles to unpick. But here is the simple fact that gives the so called Corbyn effect its charge, and which made a Tuesday night in Luton so electric.

Whoever ends up being the leader of the beleaguered Labour party is not going to be decided by disgraced former prime ministers, newspaper columnists, or the rightwing forces who seem surprisingly rattled by someone they habitually claim would be an electoral disaster. Tens of thousands of people get to decide – and in times as irreverent and unpredictable as these, that means everything: literally, everything.