There are few things most politicians hate more than a crude yes-or-no question. But when asked last autumn if he was instinctively a yimby rather than a nimby – meaning someone enthusiastically in favour of new housing in their own back yard, rather than a foot-dragging objector – for once Keir Starmer answered unflinchingly in the affirmative. It’s rare for Labour to say an unhesitating yes to anything lately, instead of hedging that actually it’s a bit more complicated than that, or else too expensive. The plan to build 1.5m new homes in five years is both those things with knobs on and yet somehow – feel free to touch wood here – it’s one of the last genuinely big Labour ideas not to get its wings clipped. Ed Miliband’s green deal lost its £28bn price tag en route to government, and the CBI is visibly gunning for Angela Rayner’s package of workers’ rights. But planning reform and mass housebuilding, for social rent and to buy, is expected to remain a centrepiece of the manifesto, and not just because it’s central to Labour’s plans for economic growth. This will be the first election in which millennials, not baby boomers, are the biggest grouping by age in more than half of constituencies, and with that comes the wind of change. Power is shifting towards a generation unjustly priced out first from home ownership and increasingly now from private renting too. That helps explain why housing is the top issue in a quarter of Labour’s most winnable constituencies, while an analysis this week by the market researchers Stack Data Strategy suggests voters in the places Labour actually needs to win a majority – mostly towns and suburbs, not the rural shires that spooked the Tories into dropping mandatory housing targets – are more pro-development than others. Middle England’s wrath is not necessarily what it was. Research for the Fabian Society, meanwhile, shows 58% of voters in England and 74% of Londoners favour at least some building on the green belt around big cities. While the phrase “green belt” conjures up emotive images of rolling meadows, Labour has ingeniously rebranded the bits it wants to release for development as “grey belt”: think disused car parks and unloved wasteland on the edge of big cities. It’s thought at least one of the five Milton Keynes-style new towns Labour wants to build could be a so-called “urban extension, and though any site identified is likely to meet local resistance, Labour hopes five big battles will be easier to fight than endless small, scattered disputes over tacking housing estates on piecemeal here and there. But, all that said, it’s naive to think any of this will be easy in practice. The lesson both from the last Labour government’s failed attempt to build five new ecotowns, and more recently from Tory housing ministers’ doomed battles with their own backbenches, is that the road to hell is paved with missed targets. Nimbyism won’t evaporate overnight just because a Tory MP in a marginal seat is replaced by a Labour MP equally scared of being unpopular. A leader as wary as Starmer often is of confronting resistance head-on will need a strategy for defusing it. Though he was happy to call himself a yimby, there is some internal nervousness about the tag. It was originally coined in California, where rocketing property prices (fuelled by tech industry wages) sparked a furious backlash and a radical movement for planning reform. But the US’s yimbys have faced accusations of prioritising middle-class flat-buyers over poorer renters, and alienating potentially sympathetic older Americans with aggressive rhetoric and bullish tactics. There is potential for the housing debate in Britain to become dangerously polarised too, given the understandable pent-up fury of the priced-out, and Tory MPs’ attempts to drag immigration into it by arguing that council houses should be reserved for the British-born. What implacable nimbys and militant ultra-yimbys have in common is that they both represent a small, if noisy, minority. So expect Labour to pitch its plans squarely at what might be called the “mimby” tendency instead: the bigger mass of “maybe in my back yard” types, who aren’t necessarily very politically engaged, and are anxious about a new estate on their doorstep, but are open to persuasion. Since they’re already waiting weeks for a GP appointment or commuting on overcrowded trains, mimbys are frightened of new housing piling even more pressure on public services. But they understand that new houses have to go somewhere, and worry about their children being priced out. They’re the voters the former Tory housing minister Brandon Lewis was describing when he pointed out that extensive housebuilding in his Great Yarmouth constituency never stopped his majority rising: most people, he argued, actually “don’t care” that much. The real snag is that the schemes mimbys like best – bespoke and beautiful rather than mass-produced and ugly, with lots of affordable starter homes and neighbourhood improvements into the bargain – may ultimately be viable for developers only if the land can be bought cheaply. Though Labour has floated plans to bring land prices down by reducing the compensation paid under compulsory purchase orders, crucial detail is still pending. Will all this enable Starmer to succeed where so many others have failed? Living in sleepy rural Oxfordshire, I’ve certainly seen fierce resistance to housebuilding fade surprisingly fast once the previously unwanted houses fill up with people who turn into neighbours and friends. But I’ve also seen candidates from all parties stumble, mumble, and say whatever they think local people want to hear about development, both at hustings and on the doorstep. To double the current rate of building may require backbones of steel. But this is potentially a totemic policy, rich with meaning beyond the technical sum of its parts. One reason New Labour swept to power on such a wave of excitement in 1997 is that it felt like the beginning of a new era, not just a new government. Tired old men in suits gave way to a more modern, younger, diverse cabinet that matched the national mood. Keir Starmer isn’t going to be able to pull off that trick against Rishi Sunak. But rising to meet the expectations of that millennial moment, as a younger generation with different worries starts to become dominant in British society, offers perhaps the closest thing to it. Build houses, and you’re building lives and futures. But more than that, you’re building hope. Gaby Hinsliff is a Guardian columnist