Can we trust the US election polls? | US News

Ask most party strategists, pollsters or pundits in the US and they will tell you that the 2024 presidential election could be the closest election in decades, if not a century.

Given that Joe Biden’s 2020 victory was decided by fewer than 45,000 votes in just three battleground states, that’s quite a claim.

However, that is what the polls suggest. The competition between Kamala Harris And Donald Trump is super tight, both nationally and in key states.

How much can we trust the polls?

That’s a question many are asking themselves after famously making a big mistake four years ago.

The American Association for Public Opinion Research called it the biggest election error in 40 years, showing that Mr. Biden’s lead over Mr. Trump in the final two weeks of the campaign was twice as large as it was when votes were counted.

In 2012, pollsters significantly underestimated Barack Obama’s lead over Mitt Romney. But while Mr. Trump’s victory over Hillary Clinton in 2016 shocked many people, the error in national polls was relatively small by comparison.

Of course, all polls are subject to uncertainty and some built-in errors, and they are only a snapshot of the current situation, not a prediction of the outcome on election day.

Crucially, there is evidence that they are also becoming a more reliable predictor of outcome as we get closer to the election. It may seem obvious, but a year after the vote, polls are on average seven points different from each candidate’s final tally. By the last week of the election campaign, this value had fallen to less than three points.

Every day the polls tell us a little more about the result.

So how should we read them?

An important point to remember is the uncertainty surrounding estimated support for the candidates.

Uncertainty: “Margin of Error”

While pollsters each release a percentage, they also provide a “margin of error” to indicate how much support might vary.

For example, if a poll puts Mr. Trump at 46% with a margin of error of three percentage points, that means his support among the electorate is likely to be between 43% and 49%. If Ms. Harris is at 49% in the same poll, then her support is likely to be between 46% and 52%.

All of this tells us that the competition is approaching and one of the two candidates could come out on top.

Similar caution should be exercised when considering trackers that use survey averages.

One might think that averaging the surveys would reduce uncertainty because random errors should cancel out. However, some pollsters are consistently more accurate than others, while others may be systematically wrong in one direction. Add them all together and these biases can be reinforced.

Read more about the election:
What exactly happens on the night of the US election?
How does Donald Trump keep his support so strong?

Predicting Voter Turnout: Context Matters

Who votes in an election also determines the outcome, but predicting this is a difficult task for pollsters. About a third of eligible Americans don’t vote in presidential elections, and it’s not always the same people.

The context is important. It can make people more or less likely to vote. For example, possible changes to abortion laws appear to have mobilized many Democrats in the 2022 midterm elections.

A candidate’s policies and performance can also influence the likelihood that more partisan voters will turn out.

The Electoral College: Why State Elections Can Matter

The same considerations are necessary when looking at state polls and are arguably more important in determining which candidate is most likely to win the election.

The outcome of a presidential race is decided state by state by the Electoral College, and the difference between that vote and the national vote has grown ever larger.

Read more: What is the Electoral College?

In 2000 and 2016, the candidate with the most votes statewide lost the election because he did not win the combination of states that produced the most votes in the Electoral College.

This is why battlefield polls receive so much attention and are included in the models of statisticians trying to predict the outcome.

Of course, they have the same uncertainties and potential flaws as national surveys. And the bad news is that their recent performance hasn’t been great.

In 2016, they suggested Clinton would win the key states needed for a comfortable victory in the Electoral College. In 2020, they fared even worse.

It has proven particularly difficult to conduct accurate polls in some states. In 2016 and 2020, the biggest failures occurred in Wisconsin, Michigan, North Carolina and Pennsylvania.

These, particularly Pennsylvania, which has the most Electoral College votes of the group, are all potentially crucial in 2024.

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So what can the polls tell us?

The answer is sufficient if you’re looking for an overview of how people feel about a particular candidate or policy.

However, if you’re trying to figure out who is ahead in the race for president, the only thing you can be sure of is that the contest is very close and could come down to a small vote count in some states.