The seeds of the Tory collapse were sown in 2019

This is the first in a Data Points series on the UK election

As things stand, when Britain goes to the polls in less than four weeks the Conservatives are set to lose somewhere between 7mn and 9mn of the 14mn votes they secured in 2019. The final result is likely to be the party’s lowest ever share of both votes and seats.

This outcome would have been completely unthinkable five years ago, when Boris Johnson delivered the Tories’ largest majority in 30 years. But should it have been?

It is notable that support for the Tories since 2010 was generally sustained or rising for the first nine years — despite austerity and enduring economic stagnation — before turning sharply in early 2020 and marching steadily downwards. The pandemic lockdowns, the “vaccine bounce” in the polls, the partygate scandal, even Liz Truss’s infamous “mini” Budget: all are mere blips on a clear linear trend.

How can we explain such a sharp inflection point?

One key part of the puzzle is that Johnson’s victory was much flimsier than it first appeared. Conservative voters in 2019 — especially those who defected from Labour — were motivated primarily by two things: getting Brexit done, and keeping the opposition’s Jeremy Corbyn away from power, not by deep support for the Tory party.

With Corbyn gone and the Brexit deal signed, the two strongest ties between many voters and the Conservatives were cut. As the political sociologist Paula Surridge points out, less than a year into power, the Tories had already lost a fifth of their support. The danger signs were there.

A striking statistic in British polling is that the Labour party has led in two-thirds of the 4,000 opinion polls published during the past 14 years of Conservative government. The Tories, though, have led when it mattered.

But ironically, a focus on public opinion has been central to the Tories’ recent undoing. In the battle between “popularism” (proposing policy that commands majority public support) and “deliverism” (actually getting things done), the Conservatives have time and again opted for the former over the latter in the hope of a quick fix in the polls, with increasingly dire results for both party and country.

This government will be remembered for ballooning NHS waiting lists, school roofs falling in, prisons overflowing and projects being cancelled. But, by Jove, the policies polled beautifully in isolation.

The Tories’ 2019 manifesto could not have been better calibrated to appeal to every type of voter. There was levelling-up for the “red wall” voters in traditionally Labour areas, increased NHS funding for the left, net zero for the environmentally conscious, tax cuts for the Tory base and new restrictions on immigration to fend off the challenge from the right.

The Conservatives’ great strength in the 2019 campaign was being all things to all people. But after four and a half years of repeatedly failing to deliver them, that’s a lot of different groups left disappointed.

Fewer than half of their key original manifesto pledges have been met, a marked decline in competence compared with earlier governments. Today only 9 per cent of voters say the Tories keep their promises, down by two-thirds since the eve of the 2019 election. And almost all of the decline in trust in Britain’s politicians over recent decades has come in the past five years.

The problem with making lots of different, incompatible promises to lots of different people is that when you fail to deliver on them, you upset them all.

The result has been a haemorrhaging of votes in all directions. Parties usually trade off voters on one flank for the other. In 2015 David Cameron lost ground to Ukip on the right but won over liberals and Labour voters. Rishi Sunak is losing millions to the left, right and centre all at once.

In his historic 1997 defeat to Labour, John Major held on to 60 per cent of voters who had backed the Tories five years earlier, rising to 70 per cent of those with the most socially conservative views. His party was humbled, but its base remained intact.

Fast forward 27 years, and Sunak, by incurring steep losses on both flanks, is currently holding on to just 43 per cent of 2019 Tory voters.

The Conservatives’ 2019 voter coalition was a short-term loan. It is being paid back with interest.

john.burn-murdoch@ft.com, @jburnmurdoch