Pros and cons of political polling

The accuracy of political opinion polling is being hotly debated as US voters prepare to go to the ballot boxes.

Wildly differing polling results ahead of next week’s US midterms mean that “everything from a Democratic hold in the Senate and a narrow House majority to a total Republican rout” is “imaginable”, said The New York Times’s chief political analyst Nate Cohn.

Pollsters in the US have faced widespread criticism in recent years, after calling the 2016 presidential election wrongly for Hillary Clinton, before underestimating support for Donald Trump once again in 2020. And while UK polling this summer suggested that Rishi Sunak stood no chance against Liz Truss in the Tory leadership race, the result ended up being much closer than expected.

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Similar polling inaccuracies in countries worldwide have fuelled debate about whether a new approach to both gauging and reporting public opinion is needed. And what could happen if opinion polls during election periods were banned?

1. Pro: better gauge than social media

Polling is “the most effective way of obtaining voters’ opinions or concerns on key issues or voting intention”, according to Jouni Kuha, a professor in LSE’s Department of Statistics. Although other sources of data such as social media can “provide some insight to decode voters’ behaviours”, they are “unlikely to be as good a source for predicting voter intention or election outcomes”, Kuha wrote.

2. Con: inaccurate results

Polls in the UK have a “history of inaccurate performance”, wrote Nate Silver for FiveThirtyEight, with average errors that are more than double those in American presidential elections. For instance, explained Roosmarijn De Geus for OxPol, in 1992, “the polls predicted a Labour lead only for the Conservatives to win a majority at election day”. In 2010, polls drastically over-estimated the popularity of the Liberal Democrats, and in 2015 polls overestimated support for Labour and underestimated support for the Tories.

3. Pro: reduces elitism

Without opinion polls, the discourse in the run-up to elections would be dominated by an elite of pundits and journalists, whose predictions and commentary could be at least as flawed as that of any snapshots of wider public sentiment. Polling “gives the people a chance to speak for themselves instead of letting only vocal media stars speak on behalf of all”, said pollsters Gallup and “gives people who do not usually have access to the media an opportunity to be heard”.

4. Con: risk of leading questions

In the British political drama To Play The King, an opinion pollster called Sarah Harding is challenged by a politician named Tim Stamper. “You get the answers wrong, don’t you?” he says. She replies “I can get you any answers you like, Mr Stamper. That’s why I’m in such demand.” Concern over leading questions has long dogged the polling industry and was depicted humorously in the political comedy Yes, Prime Minister.

5. Pro: strategic voting aid

Surveys have been found to help bewildered voters hone their decision. Polls can “provide voters with valuable information that allows them to vote strategically, especially in primaries where you’re less likely to know a lot about the candidates”, wrote Maggie Koerth for FiveThirtyEight. For instance, if you are a Democratic primary voter in the US who likes two hopefuls, poll findings can help you decide “which of those two candidates is most likely to benefit from your vote”, argued Koerth.

6. Con: bandwagon effect

However, the above trend comes with obvious downsides. The “bandwagon effect” happens when people vote for the party they think is going to win, while the “boomerang effect” sees voters evaluate a party more negatively if a poll suggests their chances of winning are low. Either way, an opinion poll has influenced, as well as reflected, public opinion. “Some countries impose an election silence that halts polling because of a belief that the bandwagon effect tilts the democratic process,” wrote Mark Balnaves on The Conversation.