By the end, it had become less a byelection, more a mythical quest. Whoever could draw the sword from Makerfield’s stone – or more prosaically, beat Reform in a seat where it practically swept the board in last month’s local elections – would claim the divine right to rule the Labour party. And lo, on Friday morning, Andy Burnham became the chosen one.

He carries the magic shield of not being from Westminster – though that won’t last, obviously – plus the easy warmth with people that Keir Starmer lacks, and the rare ability to generate excitement in politics. Reform is beatable, and the sun shines brighter for knowing that. A third successive defeat for Nigel Farage in a winnable byelection, after losing Caerphilly to Plaid Cymru and Gorton and Denton to the Greens, suggests a trend, not a fluke.

Less obviously, Burnham’s good-natured campaign also helped the country see another side of places like Makerfield, beyond the day drinkers furnishing visiting journalists with blood-curdling quotes; a side where the Reform candidate’s sexist comments still hurt him and people with tough lives might still give a mainstream politician a chance. Another future is still possible. But only if Burnham shows he can genuinely govern as well as win.

For Starmer was a winner two summers ago, swept to victory on similarly heady but vague promises of change – and look at him now. The last loyalists began peeling away shortly after John Healey’s shock resignation as defence secretary, over yet another prime ministerial failure to take a decision. It’s over for Starmer, essentially. Barring a currently unlikely rush among Labour MPs to embrace Wes Streeting, the question now is how to bridge the gap until Burnham is ready. For turning the kind of post-industrial, leftwing populism that worked in Makerfield into a coherent national project will take some work.

Despite the snark about his supposed flip-flopping, Burnham’s values haven’t changed since I first got to know him professionally, nearly 30 years ago. He’s a small-town lad from a close-knit Catholic family, who married his university girlfriend and still has something of the wide-eyed altar boy about him. Though his faith has lapsed – he consistently votes pro-choice and pro-LGBTQ+ rights – the church shaped his family’s sense of doing right by others and provided a childhood sense of security, alongside his other religions of football and music. It was as a young cabinet minister, in 2009, that he first properly channelled all that into politics, when the shock of being booed on the anniversary of the Hillsborough disaster jolted Burnham into publicly battling for an inquiry.

But if his roots matter, he also has the chameleon qualities and slightly chippy confidence of the state-school-to-Cambridge kid who had to learn to fit into places he didn’t seemingly belong. His great strength is his empathy: he’s unusually sensitive to people’s underlying emotions – and unafraid of mirroring them. His instinctive gut reaction during the pandemic, to Manchester being repeatedly pushed back into restrictions, went viral because it nailed the feeling of being punished for higher Covid rates driven by inequalities and forces that people felt powerless to control. If other politicians find him ideologically hard to read, the public doesn’t.

That same empathy, however, means he struggles to say no. Every rival Labour faction sees something to like in Burnham, from his Blue Labour-tinged communitarianism to his enthusiasm for electoral reform or his socialist embrace of bringing public services into public control (which doesn’t stop him retrospectively defending the private finance initiative). But they also all see chances to change his mind. That leaves an awful lot of cooks now jostling to stir the broth.

In the north, he resolved the contradictions through what he called a politics of place, reliant on deeply knowing your community – from cosmopolitan central Manchester, through its more conservative suburbs to struggling peripheral towns – and setting aside partisan differences in order to rebuild a sense of pride and belonging. If he could somehow translate this benign form of identity politics from Manchester to Britain at large, it would be an extraordinary achievement. But for now, that’s a superhuman task lacking a detailed plan. Having campaigned literally in poetry – his closing campaign video was a moving recital of Lemn Sissay’s elegiac Anthem of the North, originally written for Newcastle – he needs a summer of knuckling down to the small print.

Where exactly does he stand on immigration? In Makerfield, he backed Shabana Mahmood’s hardline reforms. But a Labour revolt is already brewing against them, with Angela Rayner campaigning particularly vociferously against the policy of making it harder for people who came to the UK to work as carers to settle permanently. Does Burnham, whose genuine desire to fix social care dates back to unfinished business as health secretary in the Brown government, really want to drive migrant care workers out of an already threadbare system? What’s his answer to his rival Streeting’s argument that Labour shouldn’t be afraid of making the positive case for immigration?

Big questions still loom, meanwhile, over borrowing, tax, spending on welfare and defence versus net zero – especially if Ed Miliband becomes chancellor – and what exactly “business-friendly socialism” means for, say, regulating big tech. Does Burnham mean what he says about sticking to Rachel Reeves’ fiscal rules and tax pledges, and if so, what room does he realistically have left for radicalism? Though taking public control of transport, water and energy was Burnham’s most popular policy in Makerfield, Starmer is already renationalising the railways and hinting at a possible takeover of Thames Water for precious little electoral reward – perhaps because people haven’t yet felt the difference in their pockets.

Burnham’s operation is relaxed and freewheeling, and he remains suspicious of attempts to impose more order now. But while in Manchester he has relied on a small, trusted circle to hammer out the detail of his big ideas, in Downing Street he’d have to manage experienced cabinet members with agendas of their own, plus a Whitehall machine requiring crystal clear direction to deliver. He’ll need help rebuilding bridges with MPs, too, as he shifts from years of blaming Westminster for not getting it to being the one that everyone outside Westminster blames.

Nobody wants to rain on this parade of hope. But a frictionless coronation in which the party politely ducks awkward questions will ultimately do Burnham no favours. Contest or no contest, Labour must find ways of stress-testing his ideas over summer, plugging holes that might otherwise be painfully exposed in office. And then crucially, come September, it must do its level best to make what’s left work. Andy Burnham may just have earned Labour a second hearing. Squander that chance, and there won’t be a third.

• Gaby Hinsliff is a Guardian columnist