The 2024 election is shaping up to be the most opinion-poll-heavy ever in the UK. And when so many polls are flying around, it can start to feel like they are setting the agenda as much as measuring the mood. It is often claimed that being routinely reminded that lots of people intend to vote for a party can drive others to support them, too.
In the case of the 2024 election, this would mean that Labour, ahead in the polls for over a year, would be gathering more support just by virtue of being ahead.
But, look into the evidence on whether such a “bandwagon effect” exists and you might be left wanting. And if any such effect exists, it could be more likely to result in a surge for Reform UK.
In the first few weeks of the campaign alone, more than 30 vote intention polls were published by members of the British Polling Council, an organisation that promotes quality polling. Beyond so-called “house effects”, which see pollsters differ from each other on the precise numbers, the story told by these polls has been consistent throughout. The Labour party is well ahead of the Conservatives, and Rishi Sunak’s party shows little sign of making up the ground.
Here are three things that we know about how such polling does – and does not – change an election campaign.
1. Poll leads can suppress turnout
While all parties rightly want to take the lead in the polls, being ahead can be something of a mixed blessing. Information conveying certainty about an election outcome can suppress turnout, which is something Labour might want to keep an eye on, especially in seats it is defending. Recent research shows that when a party leads significantly in the polls, lower turnout is detrimental to its incumbent MPs. Perceiving the election as a foregone conclusion could encourage complacency among Labour supporters in Labour strongholds.
It has been claimed that in the 1948 US presidential election, when the polls infamously inspired the erroneous headline “Dewey defeats Truman”, supporters of the losing Republican candidate (Dewey) “felt their candidate would win so they played golf that day”.
While it is unlikely that the polls alone suppressed Republican turnout enough to sway the overall result of the election, reminding voters that an election performance on par with current polling requires their participation may be a wise move.
2. Reform could benefit from poll momentum
Others interpret the “Dewey defeats Truman” case differently, pointing out that although Dewey led in the polls throughout the 1948 campaign, Truman gained ground over time, halving his opponent’s lead a fortnight out from the election. This momentum in itself might have contributed to Truman’s success.
We know that changes in a party’s polling performance can significantly raise voters’ expectations of its chances of winning. Research from the Netherlands, Denmark, and Germany even suggests that these changes can produce a dynamic bandwagon effect, in which people support a party not because it is the most popular, but because it is becoming more popular.
So, to the extent that Labour’s constant large lead in the polls produces further electoral benefits for the party, it may be as much about preventing the Conservatives from gaining momentum as about bringing voters onto its own bandwagon.
The party with the most notable momentum right now, and the most likely to benefit from the dynamic bandwagon effect, however, is not the Conservatives but Reform UK.
The rightwing party has been boosted by newly appointed leader Nigel Farage’s announcement that he is running as a candidate in the election. Psephologists anticipate that any increase in Reform UK’s vote share will eat into the Conservatives’ share, not only further consolidating Labour’s lead, but making that lead matter in key constituencies and costing the Conservatives many seats.
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Some even speculate that we could, in the very near future, see Reform UK overtake the Conservatives in the polls. Leapfrogging the Tories into second place could certainly give Reform UK a rhetorical advantage in being able to pitch itself as the party with momentum.
3. The bandwagon effect is overhyped
The sheer volume of polls in this election might concern those who think that the polls affect voters’ behaviour. A House of Lords select committee report has even cited the bandwagon effect as a reason for toughening up oversight over polling.
In truth, however, there is very little evidence that polls produce this kind of effect. A recent large-scale study spanning multiple countries found that those exposed to polls in simulated election campaigns were no more likely to support the leading party than those who received no polling information, reinforcing decades of research finding little-to-mixed evidence of bandwagon effects.
This lack of a bandwagon effect doesn’t seem to be due to how much attention people are paying to polls. Voters tend to have a good sense of how parties are currently polling: most can accurately identify who is in the lead, and many attribute that knowledge to the polls. So, by now, many British voters probably do know that Labour has a big polling lead, but that knowledge in itself is not likely to convince many of them to jump on the bandwagon.
In reality, Labour’s lead in the polls is so large that it is unlikely any of these effects would make much of a difference to its chances of winning the election. While the polls do seem to influence the vote, they mostly just measure it.
But if Labour wants its lead to work in its favour, it should avoid relying on simplistic ideas about the bandwagon effect. To the extent that Labour’s campaign incorporates its polling performance, it should carry on warning against complacency and doing everything it can to prevent the Conservatives from gaining any momentum – with a little help, perhaps, from Reform UK.