General election polls: How do they work and could they be wrong?

In brief…

• Rishi Sunak appears to have a mountain to climb to narrow the gap on Labour leader Sir Keir Starmer, who is storming ahead in the polls.
• But history has shown that predictions don’t always come true, with some surprises where pollsters have got it badly wrong
• Polls always contain margins of error and can never be 100% accurate

What is a voting intentions poll and how do they work?

YouGov’s voting intentions poll asks the question: “If there were a general election held tomorrow, which party would you vote for?”

People who respond to the online survey have the option of any political party fighting to win seats in the UK general election on 4 July.

Polls like these, which can also be done via telephone interviews, typically sample more than 1,000 people.

To make sure the results are representative of the entire country, pollsters then weight the results to match the demographic make-up of the UK by comparing what they’ve got with bigger sample sizes, such as census data.

Others, like IPSOS Mori’s latest MRP poll, use far bigger sample sizes from the off, with over 20,000 people. It predicted a Labour majority and three seats for Reform UK.

Percentage point leads are worked out by aggregating the results from various pollsters.

It looks like it could be bad news for Sunak, as an average of 42% of respondents have said they will vote Labour compared to 21% for the Conservatives. That means the Tories trail by 20 percentage points.

Are they accurate?

There is always a degree of error as the results get weighted, so polls can never be 100% accurate.

Many people may also choose not to reveal their true intentions, muddying the real picture of public opinion.

As Morgan McSweeney, Sir Keir Starmer’s director of campaigns, puts it: “Polls do not predict the future. Nobody has voted in the general election.”

And there have been plenty of times when the pollsters have got it badly wrong.

When have they gone wrong?

Just think back to David Cameron’s 2015 re-election campaign, where opinion polls got nowhere near the real result.

Most of the polls during the campaign put the former Conservative leader as neck-and-neck with Ed Miliband, the Labour Party leader at the time.

But when the Tories secured an overall majority for the first time since 1992, rumours of a suspected hung Parliament were left dead in the water.

Speaking of 1992, that year Labour’s Neil Kinnock was expected to trounce John Major of the Conservatives.

But what happened? Kinnick lost despite the polls being heavily stacked in his favour.

What do the polls say now?

Starmer is firmly ahead of Sunak, who is trailing by a staggering 20 points and has been struggling to narrow the deficit.

Worryingly for the Tories, some pollsters say they are heading for “electoral extinction”, with the party tipped to win just 72 seats compared to Labour’s 456, according to a Savanta Poll for the Sunday Telegraph.

Meanwhile, another bleak YouGov poll for the Tories put Reform UK on 19%, a point ahead of the Conservatives.

What do the News Agents think?

Lewis Goodall’s take: “The latest polls suggest that if the election were held today, the Conservatives would not just lose, they would not just lose badly a la 1997, they would be decimated to a rump force of around 70 seats.

“But it is worth remembering what a massive electoral mountain the Labour Party has to climb.“

Jon Sopel’s take: “We probably won’t have seen anything like this in Britain since the Ice Age…because frankly what you are looking at is a near extinction level event if the polls are right.

“And your heart says ‘that can’t be right, the Tories are here forever, they can’t be going down the toilet like that. But your head says, it’s possible.”

Listen to the latest episode of The News Agents podcast now.