DES MOINES — A highly anticipated poll of Iowa Democrats, set to be released two days before the presidential caucuses, was shelved on Saturday night because of concerns about irregularities in the methodology.
The apparent problem, raised by aides to Pete Buttigieg, prompted CNN to cancel an hourlong special organized to release the results of their survey, conducted with The Des Moines Register.
The results were held back after the Buttigieg campaign said that an Iowa supporter received a poll phone call from an operator working for the polling operation, but that the name of the former mayor of South Bend, Ind., was not listed on the menu of options, according to a senior official on Mr. Buttigieg’s campaign.
The poll is conducted by telephone from a call center, where operators read from a prepared script of candidates’ names to determine who a voter plans to support. One operator had apparently enlarged the font size on their computer screen, perhaps cutting off Mr. Buttigieg’s name from the list of options, according to a person familiar with the incident who did not have permission to speak about it publicly.
After every phone call, the list of candidates’ names is randomly reordered, so Mr. Buttigieg may not have been uniquely affected by the error, this person said. But the poll’s overseers were unable to determine if the mistake was an isolated incident.
The survey, published by The Des Moines Register for 76 years, is considered the gold standard for polling in the notoriously hard-to-predict state and is carefully watched as an early indicator of strength in the caucuses.
David Chalian, CNN’s political director, said on-air that CNN and The Register decided “out of an abundance of caution” not to release the poll after the network learned of a potential problem with the way the survey was conducted.
“It was brought to CNN’s attention earlier this evening that somebody who was questioned for the survey raised an issue with how their interview was conducted,” Mr. Chalian said. “We weren’t able to determine exactly what happened during this person’s interview and we don’t know whether it was an isolated incident.”
This supporter then relayed what had happened to Mr. Buttigieg’s campaign, which contacted J. Ann Selzer, a respected Iowa-based pollster whose company conducts the poll, about it. But the Buttigieg aide, who requested anonymity to discuss a private conversation, said the pollster offered little information about how many surveys the one-time Iowa front-runner was left off.
Carol Hunter, the executive editor of The Des Moines Register, said the newspaper could not confirm “with certainty” that the polling irregularities were limited to one respondent.
“It is imperative whenever an Iowa Poll is released that there is confidence that the data accurately reflects Iowans’ opinions,” she wrote, in a statement on the paper’s website.
Iowans typically finalize their choice late in the campaign, often deciding in the days before the caucuses occur. The late-breaking nature of the state’s political culture lends the poll outsized influence, with the power to fuel a last-minute surge in the state or can be an early dirge for candidates struggling.
Ms. Selzer called the cancellation “heart-wrenching.”
“Because of the stellar reputation of the poll, and the wish to always be thought of that way, the heart-wrenching decision was made not to release the poll,” she said in a statement on Saturday night. “The decision was made with the highest integrity in mind.”
Recent surveys have shown a fluid race, with Senator Bernie Sanders gaining momentum as other leading candidates trail close behind.
The poll was scheduled to be released as the leading candidates were making the final push toward Monday’s caucuses, the beginning of the nominating process to select the Democratic nominee. Candidates crisscrossed the state Saturday, several of them targeting Mr. Sanders, who was leading in the last Register poll several weeks ago and also recently topped a New York Times/Siena College poll last week.
Art Cullen, editor of The Storm Lake Times and a prominent figure in Iowa news media, said in an interview on Saturday, “In my eyes, it really affirms my faith in The Register’s judgment.”
Mr. Cullen said he did not envy the paper’s decision to cancel a poll that is a national calling card for the publication. But he praised The Registers’ editors for making a tough decision in the name of journalistic integrity.
“I hope people understand that they’re sticking up for accuracy and it enhances their position, and that people don’t go nuts on Twitter and trash them,” Mr. Cullen said. “They just don’t need this, and Iowa doesn’t need it.”
At least one candidate immediately sought to exploit the uncertainty arising from the scrapped poll. Taking the stage in a Des Moines hotel ballroom, Andrew Yang told an audience dotted with black-and-white “Math” hats that the sudden cancellation had fueled all manner of rumors.
And then he shared one of them.
“They said they’re not releasing it and we’re like, ‘What happened? What happened?’” Mr. Yang said, adding, “One of the rumors that we’ve gotten is we did really, really well in that poll.”
Alexander Burns contributed reporting.