Labour put 'safe' seats at risk to target marginals. It paid off – but there’s a cost | Robert Ford

The asteroid hit at dawn. The seats of four Tory former prime ministers – Cameron, May, Truss, Johnson – fell in an hour at around 6am on Friday, capping a historically unprecedented collapse for the Conservative party. The defeat of Truss provided this election’s biggest “Portillo moment” , as the political career of the country’s shortest-serving PM ended with her defeat by the largest swing to Labour ever recorded.

The loss of those four seats epitomised the message sent by voters – an emphatic rejection of the party these PMs had led over the past 14 years. The 2024 election saw the Conservatives fall to their lowest ever vote share and lose 252 seats – more than any government has ever lost before. In seat after seat, across every region of the UK, Tory MPs were swept away. An even greater catastrophe was only narrowly averted – more than half of the remaining 121 Conservative MPs clung on with majorities of 8% or less.

This unprecedented collapse was the result of a colossal proportional swing against the government. The Tories fell furthest where they started strongest. And what a fall it was. The party fell by an already substantial 9 points in its weakest seats, but in strongholds where the Tory vote began over 55% the average decline was a staggering 27 points.

As the Conservatives were swept out, Labour were swept in. Keir Starmer achieved the second largest seat gain ever, surpassed only by Clement Attlee in 1945, and the second largest Labour majority ever, surpassed only by Tony Blair in 1997. Yet while Starmer can now take his place next to Attlee and Blair as one of the great Labour election winners, his was a hollower triumph. Labour’s vote share was under 34%, up just two points on their heavy defeat in 2019, and the lowest share for a majority winning party in electoral history.

The mismatch between Labour’s anaemic vote haul and colossal seat gain reflect an election where voters were scattered to the winds, and the electoral system played a larger role than ever before. While the Conservatives collapsed everywhere, the parties advancing were many and varied, with Reform UK, the Greens and the Liberal Democrats all breaking electoral records. And the Tory collapse in England and Wales was matched by an SNP slump in Scotland, with a huge swing against the nationalists, who lost 38 of their 47 seats. Never before have so many tales of triumph or disaster unfolded in the same night.

A scattered vote magnified the role of electoral geography and the impact of the electoral system. Reform UK’s four million votes, spread evenly across the country, are now represented by just five MPs, while the Greens’ nearly two million voters have four. The Liberal Democrats, with half a million fewer voters than Reform, won 72 seats, increasing their seat haul nearly ninefold despite virtually no rise in overall support.

But even these effects pale next to the impact of first past the post on Labour. Under Starmer, Labour have made improving the efficiency of Labour’s vote a central goal, seeking to emphasise the values and priorities of voters in marginal target seats, even if this means downplaying those of voters in Labour heartlands. Last week they succeeded beyond his wildest dreams, as Labour won a towering Commons landslide on just over a third of the vote.

Geography and fragmentation are both crucial to understanding how this was achieved. The proportional decline in Conservative vote generated record swings in the Tory heartlands. The impact of this was then further magnified by intense tactical voting, with both the Liberal Democrats and Labour advancing most where they were the local opponents to the Conservatives in winnable target seats.

The confluence of proportional swing, well-placed opponents, and tactical voting was lethal. Seat after seat where the Conservatives have not lost for a century or more fell: Poole, Ashford, Tunbridge Wells (not lost since 1931); Bicester, Banbury, and Basingstoke (not lost since the early 1920s); Horsham, Henley and Mid Sussex (not lost since 1885). This was a wipeout like no other.

While Keir Starmer and Ed Davey wielded rapiers, Nigel Farage swung a great populist warhammer. More than one voter in eight backed Reform UK, but this vote was too evenly spread to win many seats. Nearly 100 Reform UK candidates came second, but just five won. Farage will be among them, with his triumph in Clacton finally delivering him a Westminster election victory for the Reform leader at the eighth time of asking.

Yet while the electoral system may mute Reform’s voice, Farage’s indirect impact was huge. Reform split the 2019 Conservative vote everywhere, and the split was deepest where it hurt most – in the heavily leave voting seats where Boris Johnson’s “Get Brexit Done” majority was built. The party won less than 8% of the vote in most remain voting seats, but more than a quarter of the vote in the seats with the largest leave vote. But with Reform support too low to deliver wins, the main beneficiaries of Farage’s populist uprising were Labour and the Lib Dems – by serving to slash Tory majorities in seats which would otherwise be out of reach.

Reform may have helped Labour in the Tory heartlands, but Starmer now has troubles in his own backyard. Labour’s vote fell on average in the seats it already held, and fell furthest in seats with large numbers of young people, graduates, and/or large ethnic minority communities.

The Greens benefited from progressive discontent with Labour. While two of the four seats the party won came in Tory areas, all 40 Green second places came in seats won by Labour. The Greens now have an opportunity to open up a new electoral front against Labour in a range of formerly safe seats where students, graduates and urban professionals cluster together.

Labour also fell back sharply in ethnically diverse seats. The Greens gained, as did independent candidates (including Labour’s former leader Jeremy Corbyn), though Labour will take heart from once again defeating George Galloway, who lost Rochdale just four months after taking it in a by-election. Two shadow cabinet members – Jonathan Ashworth and Thangam Debbonnaire – lost their seats, and there were near misses for several other senior Labour figures including Wes Streeting, Jess Phillips and Shabana Mahmood. And there was even a ray of hope for the Conservatives in seats with large Hindu populations – Leicester East (40% Hindu) delivered the sole Conservative gain of the night, while the second largest Conservative majority in the country is now Harrow East (28% Hindu).

Declines in the heartlands mean Labour are now spread thin, with more than half of their seats won with a majority of 20% or less. Labour face vulnerability on two wobbly wings; the huge haul of seats they gained from the Conservatives tend to be more economically moderate and socially conservative; and a restive urban heartland where they will face progressive pressure from a rising Green party and a band of independent firebrands. A big Commons majority may not feel so comfortable with so many MPs looking anxiously over their shoulders, and a coalition of such intense and conflicting local pressures will be hard to hold together.

In Jenga, players build taller towers by taking blocks from the bottom and balancing them on top – the taller the tower, the weaker the base. This election was a masterpiece of electoral Jenga. Labour put its heartlands at risk to throw everything – organisation, messaging, policy – at Tory-held battlegrounds. The gamble paid off handsomely, with a landslide built on little over a third of the votes cast.

But it will not take much to bring this teetering tower tumbling down. A swing of under 6% to the Conservatives would be enough to entirely wipe out Labour’s majority. Labour’s rise has been dizzying. Now they must undertake the high-wire act of government with no electoral safety net. If they fail, a brutal fall could follow, and soon.

• Robert Ford is professor of political science at Manchester University and co-author of The British General Election of 2019