Tens of thousands joined anti-austerity rallies around the country last weekend, from mainstream Labour, Greens and Lib Dems to obscure splinter Trotskyites. I talked to nurses, teachers, students and a couple of Birmingham shopkeepers, as eloquent platform speakers rightly denied the need for the next round of cuts, deeper and more brutal than anything so far. Young and old, first-time protesters alongside old hands, said they were going home to organise. The shock of the election result had galvanised them to action. But what next, and how?

Sober indignation was the tone. The Labour party has added 60,000 members since the election, but despair at parliamentary politics was there too – including the photogenic fruitcakes of Class War, who fetched up outside Downing Street, waving fists at the gates and for some reason chanting, “Let Labour die!” David Cameron and George Osborne might have leant out to give them the thumbs-up to that. Jeremy Corbyn’s strong speech in Parliament Square was greeted with loud applause, alongside Mark Steel and Russell Brand.

In comparison, people complain at how leaden the Labour leadership hustings seem. The format is a killer: the four of them in a row, given only a minute to answer each question, just time for a soundbite, but no more. What serious job interview would be conducted like that? Where is the chance to probe them on the economy, cuts, the EU referendum, health and social care? Thundering platitudes are the result: is there any politician anywhere who doesn’t proclaim they want every child to have a fair start in life? It’s not their fault the format irons the three main contenders flat. With a series of these achingly painful parades to come, let’s hope the coming television and radio hustings are better at revealing hidden depths and shallows.

Jeremy Corbyn is a good man, sincere, ascetic, beloved by constituents – but voting for him is ignoring the electorate

But the format greatly advantages Corbyn, who wins on the clapometer. He is the free spirit, the outsider not playing by the usual political rules. Unfettered by what a majority of voters beyond Islington might support in a real election, he’s a romantic, saying what no doubt many Labour members believe. Uninhibited, he makes the rest sound cautiously lock-jawed, knowing what they say now will be used against them by the Tories and their press in future.

Politics is often about symbols, not reality. Take Corbyn’s anti-Trident stand: I imagine, but I don’t know, that the potential leaders would not choose to spend tens of billions on these four submarines. But Labour is pledged to them, because any hint of unilateralism brands the party as unelectably reckless. I can argue against Trident, but Labour in opposition dare not.

Corbyn is a 1983 man, a relic of the election that brought him to parliament when Labour was destroyed by its out-of-Nato, anti-EU, renationalise-everything suicide note. He’s a good man, sincere, ascetic, beloved by constituents – but voting for him is ignoring the electorate. Goodness knows Labour faces tough dilemmas – how to win north and south, reclaim the lost votes of the old (47% of over 65s voted Tory) and win back Scotland, while fighting off Ukip in the heartlands. Every Corbyn vote gives ammunition to Labour’s enemies: Toby Young won’t be the only Tory maliciously paying £3 as a “supporter” to vote for him so they can claim Labour is back to the days of delusion.

Facebook Twitter Pinterest Labour hustings: Yvette Cooper and Andy Burnham attack Liz Kendall’s free school plans

Meanwhile, as the hustings trundle on, the government is charging ahead with its monstrous £12bn benefit cuts, hoping the savagery will be forgotten in five years. Cameron maintains the breathtaking pretence that cutting tax credits will somehow relieve instead of add to poverty, with no attempt to offer a living wage.

Nor will he safeguard disability benefits. ONS figures released later this week are expected to show that some 300,000 more children are in poverty. Gargantuan cuts in the coming budget will be the best reminder of why selecting the most electable Labour leader matters – not because of ideologies, but to put bread and butter on the tables of those driven to food banks.

It’s early days, with so many hustings still to come, but as candidates react to events between now and September, the argument between the three main contenders is shaping up. Those who say “they’re all the same” are just not listening.

Liz Kendall, fresh and relatively unknown, has disappointed some backers who hoped she’d have the dynamism of the insurgent. Her presentation has been lacklustre. She adopts totemic policies – for free schools, higher defence spending and the “centre ground”. She’s a “moderniser”, but calls for “reform” may seem a little otiose by 2020 if few services remain in the public realm. “What matters is what works” – well, yes, but who says otherwise? She has yet to show policy depth behind the words, with no flashes of Tony Blair’s 1997 radicalism – an equivalent to his minimum wage or £5bn windfall tax.

Unless she ups her game, the contest is between Andy Burnham and Yvette Cooper. His Liverpool working class backstory is a great asset. Cooper has a bit of the northern too – and the advantage that Labour needs a woman leader. The decider may be less about right and left than who has the credibility, solidity under fire, and the economic confidence and intellect to carry the argument against extreme austerity. Burnham’s interview in the Mail on Sunday seems to row back from his recent claim that Ed Miliband’s was the best manifesto he had ever stood on, resiling from some of it. Burnham was fast out of the traps to attack Osborne’s benefit cuts yesterday – but Cooper was there too, defending tax credits and calling for a living wage.

Cooper is on the up, her every outing leaving audiences thinking better of her. She even impressed the press gallery last week, the toughest gig of all. This question killed Miliband: did Labour overspending leave Britain vulnerable in the crash? Unlike Kendall, Cooper refuses to concede. It’s not true, she won’t say it and she can say why with a punchy economic explanation poor Miliband never learned. No need to choose yet: any of the three may shine brighter in the next months, but my hunch is Cooper is the one to beat.