It was a landslide election but this much is clear: neither Labour nor the Tories stand on solid ground | Aditya Chakrabortty

Don’t forget that the word landslide has another meaning, freighted with danger. Soil comes loose and the ground fails. Solid land turns semi-liquid under your feet. Without warning, rocks come crashing down. A vast river of mud covers roads, levels homes. What was once safe territory turns lethal.

No one at Westminster this week wants refreshers in geology, and who can blame them? Much more pleasant to talk of mandates, of Britain as an oasis of political stability, of the orderly transition of power in the mother of all parliaments. Yet this general election shows us that the landscape for both government and official opposition is growing ever more treacherous.

It’s not just the fact that Keir Starmer has scooped a Tony Blair-style majority on Jeremy Corbyn-style polling. It’s also that this country’s two big parties took their lowest share of votes and seats alike in more than a century. There hasn’t been such weakness at the heart of the party system since Lloyd George’s Liberals were on their deathbed.

Long before the side slides off a mountain, the conditions build up until, finally, just a little rainfall can trigger calamity. Many of the biggest names around the new cabinet are dreading a downpour in their own back yard. Consider those representing Labour’s real heartlands: the big cities, with their electoral coalition of renters, ethnic minorities and established leftwingers – a coalition that is coming apart.

Look at David Lammy in Tottenham, who lost more than 12,000 votes on Thursday. Or Starmer himself, who talked about deporting Bangladeshis, perhaps forgetting that one in 10 of his own constituents are of Bangladeshi origin; he dropped 17,000 votes. And if you think being the toast of SW1 protects you from rough music at the neighbourhood ballot box, consider Wes Streeting, who came within 500 votes of losing his seat.

So what, you might ask. Flash some left ankle and win back those malcontents. Except on the other side of the same cabinet table are those under direct attack from Nigel Farage’s troops. Think Angela Rayner, Yvette Cooper, Bridget Phillipson, Jonathan Reynolds, John Healey: all representing northern towns, all with Reform as their main opposition. Cast your eye across the valleys of south Wales, where Farage launched his manifesto.

From Llanelli to Pontypridd, Reform ran Labour a strong second in 13 Welsh seats – quite some showing for a party whose leader joined the race late. The next devolved elections in Wales are less than two years away, and already Labour people worry they may end up a victory parade for the Faragists.

A map of who won south Wales last Thursday night will, like London, be unbroken red. A map of who came second will show south Wales a big blob of Reform turquoise, while inner-east London turns Green. The electoral coalition on which Labour depends does not have one single breakaway bloc ­– it is splintering in opposite directions.

What’s the story? I see two separate threads, which are starting to braid around each other. The first has been with us for years and has had dramatic impact, such as with the Brexit vote of 2016 or the collapse of the so-called red wall in 2019. At those points, the whole of SW1 wonders why the plebs aren’t doing as they’re told.

Reporting around the country for this column since 2010 I’ve seen why, time and again. You go to a town where the big employer or major industry died decades ago. Now the coalmine is a call centre or the factories are warehouses. And the local institutions have withered away, from the unions to the newspaper to the Labour offices. And this extends way beyond politics: the latest census shows the least Christian part of England and Wales is not some urban fleshpot but a big tranche of south Wales.

This is the world described by the late Peter Mair in his classic Ruling the Void – a book about how western political parties have lost interest in the public, while the public has lost interest in political parties. Until the era of John Major, only one in five voters flipped between blue, yellow and red. Last week that doubled to two in five voters, according to Focaldata; the polling company calls it “a state of permanent revolution”.

As Keir Starmer became Labour leader in 2020, there were many agonised think pieces about how he had to find a way to speak to both Hartlepool and Hackney. In the end, he did no such thing. He chose to face Hartlepool and blank Hackney. Labour traded votes from the big cities for those from small towns. With its share of the vote in England up only half a percentage point on 2019, the party’s whopping electoral success this time round came from such efficient targeting.

Since cities are where Britain’s ethnic minorities live (more than 40% of Londoners are from ethnic minorities – not that you see many of us in our supposedly “London-centric” media and politics), this trade comes with racial consequences. It means Natalie Elphicke rather than Diane Abbott or Faiza Shaheen. It means waving union flags while calling those protesting against war crimes in Gaza “fleas”.

And it ultimately means a huge political problem, because Starmer’s team is speedily converting safe Labour territory – Muslims and other ethnic minorities – into marginal voters. None of my reporting leads me to believe that process will automatically reverse if there’s a pause to the massacres; the anger over Westminster’s disregard for brown lives in the Middle East is much more about Westminster’s disregard for brown lives in Britain.

After conducting focus groups with Muslims, Luke Tryl, director of More in Common UK, observes: “We would hear real frustration over Labour on Gaza, but very quickly it would come back to a broader point that Labour took Muslim votes for granted [and] their communities had been neglected. Very similar to what you’d hear in the red wall, post referendum.”

When the white working class started peeling off from New Labour, Peter Mandelson declared they had nowhere else to go. Except now they do. They can choose Reform, while brown working-class voters can plump for Independents or Greens – or both sides can just stay at home.

New Labour’s strategy of triangulation works brilliantly when there are only two parties to pick from. But it offers diminishing returns as our political system moves towards accommodating four or more parties.

His team could plough on, of course, with an economic growth strategy that consists of hoping for economic growth. It could ignore that big crack there in its coalition, this worrying bulge over there. But then, when they least expect it, the rocks might start falling and, soon, the ground could give way.