Donald Trump

Donald Trump speaks at the Republican Party of Iowa’s Lincoln Dinner in Des Moines on May 16. (Scott Olson / Getty Images)

David Lauter
December 20, 2015

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.

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