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Polls may actually underestimate Trump's support, study finds

Tribune Washington Bureau logoTribune Washington Bureau 12/24/2015 David Lauter
Supporters watch Republican presidential candidate Donald Trump arrive at a campaign rally, Wednesday, Dec. 16, 2015, in Mesa, Ariz. © Ross D. Franklin/AP Supporters watch Republican presidential candidate Donald Trump arrive at a campaign rally, Wednesday, Dec. 16, 2015, in Mesa, Ariz.

WASHINGTON — Donald Trump leads the GOP presidential field in polls of Republican voters nationally and in most early voting states, but some polls may actually be understating his support, according to a new study.

The analysis, by Morning Consult, a polling and market research company, looked at an odd occurrence that has cropped up repeatedly this year: Trump generally does better in online polls than in surveys done by phone.

Why is that, and which polls are more accurate — the online surveys that tend to show Trump with support of nearly four-in-10 GOP voters or the telephone surveys that have generally shown him with the backing of one-third or fewer?

Morning Consult ran an experiment: It polled 2,397 potential Republican voters earlier this month using three different methods — a traditional telephone survey with live interviewers calling landlines and cellphones, an online survey and an interactive dialing technique that calls people by telephone and asks them to respond to recorded questions by hitting buttons on their phone.

By randomly assigning people to the three different approaches and running all at the same time, they hoped to eliminate factors that might cause results to vary from one poll to another.

The experiment confirmed that "voters are about six points more likely to support Trump when they're taking the poll online then when they're talking to a live interviewer," said Morning Consult's polling director, Kyle Dropp.

"People are slightly less likely to say that they support him when they're talking to a live human" than when they are in the "anonymous environment" of an online survey, Dropp said.

The most telling part of the experiment, however, was that not all types of people responded the same way. Among blue-collar Republicans, who have formed the core of Trump's support, the polls were about the same regardless of method. But among college-educated Republicans, a bigger difference appeared, with Trump scoring 9 points better in the online poll.

Social-desirability bias — the well-known tendency of people to hesitate to confess certain unpopular views to a pollster — provides the most likely explanation for that education gap, Dropp and his colleagues believe.

Blue-collar voters don't feel embarrassed about supporting Trump, who is very popular in their communities. But many college-educated Republicans hesitate to admit their attraction to the blustery New York billionaire, the experiment indicates.

That finding suggests that the online surveys, which show Trump with a larger lead, provide the more accurate measure of what people would do in the anonymity of a voting booth, Dropp said. That might not be as true, however, in a public setting such as the Iowa caucus, where people identify their candidate preference in front of friends and neighbors.

"It's our sense that a lot of polls are under-reporting Trump's overall support," he said.

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