Pollster Ann Selzer has vowed to review the data after her weekend poll on the presidential race in Iowa turned out to be wrong by 16 points.
Though counting is still ongoing in the state after Tuesday's election, President-elect Donald Trump won the state's 6 Electoral College votes with 55.9 percent of the vote compared to Vice President Kamala Harris's 42.7 percent, per estimates from the Associated Press.
What Was Ann Selzer's Prediction?
The Iowa poll, conducted by Selzer & Company for The Des Moines Register/ Mediacom, found Harris had a three-point lead over Trump in the state, 47 percent to the Republican's 44 percent.
The poll surveyed 808 likely voters in Iowa between October 28 and 31 with its shock result falling within the poll's 3.4 percent margin of error.
Announcing her findings on Saturday, Selzer, previously described as "the best pollster in politics" by aggregator FiveThirtyEight, said Harris had "clearly leaped into a leading position."
However, the Iowa poll turned out to be wrong by 16 points following the results of Tuesday's election. The former president has won Iowa by 55.9 percent to Harris's 42.7 percent, a difference of 13.2 percent so far.
The Iowa poll also predicted that women—especially older and independent voters—would drive Harris's win in Iowa. Describing the poll results, Selzer said, "Age and gender are the two most dynamic factors that are explaining these numbers."
Newsweek has emailed Selzer & Company for comment.
What Did Ann Selzer Say After the Election?
In a statement on Tuesday night, Selzer said, "Tonight, I'm of course thinking about how we got where we are. The poll findings we produced for The Des Moines Register and Mediacom did not match what the Iowa electorate ultimately decided in the voting booth today. I'll be reviewing data from multiple sources with hopes of learning why that happened. And, I welcome what that process might teach me."
The poll caused a stir when it was published given the state had voted for Trump in both 2016 and 2020.
Trying to work out what might have gone wrong, Selzer pointed towards Robert F. Kennedy Jr., who withdrew from the race in August but remained on the ballot in the state. The Iowa poll said he would get 3 percent of the vote.
"Technically, the poll had some 'give' in that neither candidate reached 50 percent. So, the people who said they had voted/would vote for Robert F. Kennedy Jr. could easily have switched to Donald Trump," Selzer said.
"The late deciders could have opted for Trump in the final days of the campaign after interviewing was complete. The people who had already voted but opted not to tell our interviewers for whom they voted could have given Trump an edge. Maybe I can gain clarity on that 9 percent and an underlying disposition toward the presidential race."
What Did Other Pollsters Say Before the Election?
Prior to the election, FiveThirtyEight gave Trump a 93 percent chance of carrying the Midwestern state.
Pollster Nate Silver responded to the Iowa poll calling it "shocking" and commending the "guts" it would have taken to release it.
Writing in his Silver Bulletin blog, he praised Selzer as a polling "maverick," saying "in a world where most pollsters have a lot of egg on their faces, she has near-oracular status."
However, he pointed out that her poll would likely be "wrong" as other surveys continued to point to a Trump majority in Iowa.
The Trump campaign dismissed the poll as an "outlier."
In recent years, the Iowa poll has been remarkably accurate. In both 2016 and 2020, it predicted that Trump would win by 7 percentage points. He won by 9 points in 2016 and 8 points in 2020.
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