President Donald Trump’s intense, typically less engaged voter base has complicated presidential election polling in recent years, and as the election approaches without clear trends in polling data, experts are evaluating the theories behind where 2024’s polling may be accurate—and lacking.
TOPSHOT - (L to R) Senate Majority Leader Chuck Schumer (D-NY), US Vice President and Democratic ... [+]
Polling for the 2024 presidential election shows candidates in a dead heat, but experts say polling accuracy is complicated.
In 2020, presidential polling was the “most inaccurate in 40 years” and still inexplicably predicted President Joe Biden’s win by more than three percentage points of his eventual margin, with some believing the pandemic caused less survey engagement and failed to capture Trump’s support strengthening, the WSJ reported, citing a panel of polling experts.
In 2016, Hillary Clinton was widely projected to win by sweeping key “blue wall” states like Michigan, Pennsylvania and Wisconsin, but was edged by Trump in all three, and lost handily.
But the 2018 and 2022 midterm election polling were relatively accurate, further complicating pollsters' understanding of the factors at play.
Now, concerns around polling have returned as the race continues to be nearly tied, with concerns on both sides that incorrect polling figures, even a “small systematic polling error,” could unpredictably skew the results, prominent statistician Nate Silver writes in the New York Times.
Silver says, if anything, the polls show that a “surprise” is equally likely for each side, even if his “gut feeling” points to Trump’s victory.
In political polling, dozens of firms survey thousands of people in many different ways, from mail surveys, phone calls and online surveys. Often, pollsters use a combination of outreach methods. They then employ several methods to try and make polling data more accurate, such as weighting it, or interviewing tactics to ensure more trustworthy results.
Recency bias is the inclination to think the person who won most recently will win again. Voters might predict Trump will be the next president because he won in 2016. Nonresponse bias accounts for certain groups who show disinterest in taking polls. In the past, Trump supporters have tended to be less responsive to surveys and polling outreach, suggesting that polls end up underestimating them. But this year, some Democrats wonder if (and hope) polls are similarly undercounting their traditional key demographics, including Black voters and young voters.
Weighting emphasizes survey data, like a respondent’s sex or age, that pollsters believe is underrepresented. During the 2018 midterm election, pollsters weighted by education to trim state polling inaccuracies in 2016’s presidential election polling figures, which did not accurately reach voters with less education, according to the New York Times. After 2020, pollsters increasingly started weighting by “recalled vote,” or who the respondent recalled previously voting for, to make sure they were capturing enough Republicans. But some experts are concerned that emphasizing the “recalled vote” has flaws. Respondents might not remember their vote correctly and falsely record they voted for the winning candidate, according to the New York Times. For some polling operations, the “recalled vote” could inaccurately shape their predictions by reflecting opinions about a previous election. Even so, two in three polls used this technique in September, the New York Times reports.
The “Shy Voter Theory” suggests that Trump supporters are not always truthful about their voting plans, perhaps because they don’t want to admit to a pollster they support Trump. That means polls might be underestimating Trump’s popularity in the 2024 election. Some say this theory explains the inaccurate polling figures in 2016 and 2020. But it also might not affect polling today, Silver states in the New York Times. Many Trump voters are ardent public fans and have no reservations about declaring their support.
The “Bradley Effect” theory would be a boon for Trump. The theory—named after Los Angeles Mayor Tom Bradley, a Democrat who was Black, who lost the 1982 California gubernatorial race to Republican state attorney general George Deukmejian— holds that white voters who identify as “undecided” sometimes just don’t want to admit that they won’t vote for a Black candidate. The Obama campaign has advocated against this belief and somewhat disproved it by winning the presidency in 2008 and 2012 by relatively large margins. But some think this theory might apply to 2024 polls and to Harris, as the first Black woman presidential candidate. A similar, gendered effect was blamed for 2016, where undecided voters eventually tended not to vote for Clinton, Silver writes.
The “Unified Theory” explains, based on Trump voters’ inclination to ignore surveys, why presidential election polling is less accurate than midterm elections. According to this theory, polling was more accurate in 2018 and 2022 because more highly engaged voters—the ones most likely to take part in polls—participated in the midterms. In contrast, a larger pool of potentially unresponsive, less engaged voters exist and tend only to vote in presidential elections. That means the pattern from 2016 to 2020 of polls undercounting Trump voters — who are typically less engaged — could continue in 2024.
The “Patchwork Theory” says that the errors made in polling in 2016 and 2020 are entirely unrelated to each other and unrelated to midterm elections. These elections both faced a set of unique factors that led to the polls being wrong. Polls overrepresenting college-educated individuals and undecided voters pushed 2016 polls in Clinton’s favor, some argue. In 2020, the pandemic’s widespread influence on people’s lifestyles and decisions affected the polls drastically, others point out.