WASHINGTON, Nov 20: Following Republican President-elect Donald Trump's resounding victory in this month's election, some U.S. pollsters are scrambling to understand why their surveys once again underestimated his support among American voters.
Polls before the Nov. 5 vote had shown Trump trailing Democratic Vice President Kamala Harris by 1 percentage point, according to an average of dozens of national opinion polls compiled by 538, a website on data analysis for politics and sports. With vote tallies nearly finalized, Trump led Harris nationally by 2 percentage points: 50% to 48%.
That undershoot of 3 points follows polls in 2020 that underestimated Trump's national margin by 4 points and in 2016 that underestimated his performance by 2 points, according to 538's averages.
Those results are all largely within pollsters' normal margins of error -- a measure of statistical precision influenced by a variety of factors including the number of respondents to a poll -- and the narrow divide of the American electorate makes getting the call right especially difficult.
But the fact that national presidential opinion polls have persistently been off in the same direction is driving suspicion among some pollsters and polling experts that surveys are having trouble getting responses from Trump supporters, leading them to underestimate his strength.
"It's hard to escape the idea that there's a challenge in reaching Trump voters," said Charles Franklin, a pollster at Marquette Law School in Milwaukee who will be on a task force assessing pre-election polls for the American Association for Public Opinion Research, the main professional organization of experts on U.S. polling and survey research.
Even in the battleground states of Arizona, Georgia, Nevada and North Carolina - where the surveys were largely correct in pointing to Trump victories on Nov. 5 - the former president's margin on Election Day was about 1 to 3 percentage points higher than it was in the polls.
In the Rust Belt swing states of Pennsylvania, Wisconsin and Michigan - where Trump was behind in the surveys but won the vote - the polling averages similarly underestimated him by 2 to 3 points.
Vanderbilt University political scientist Josh Clinton, who led a task force analyzing how surveys performed in the 2020 election cycle, said he was worried that the apparent mismeasurement could amplify its possible cause: public distrust of polling and of political institutions writ large.
"It delegitimizes the whole operation in ways I think are pretty damaging," said Clinton, one of four leading U.S. pollsters and polling experts interviewed by Reuters who have participated in past American Association for Public Opinion Research postmortems or are due to participate in this year's exercise.
—REUTERS
