Why Donald Trump May Be Weaker Than a Recent Poll Suggests

He's in front or close among “potential GOP voters”—but that may not be who actually turn out to vote.

Donald Trump, president and chief executive of Trump Organization Inc., speaks during the Republican Party of Iowa's Lincoln Dinner in Des Moines, Iowa, U.S., on Saturday, May 16, 2015. Several current and potential candidates for U.S. president will speak during the dinner, hosted by the Republican Party of Iowa.

Photographer: Daniel Acker/Bloomberg

No matter the subject, for surveys to make sense, they have to be sampling the correct population. If you want to learn about car buyers, a researcher needs to interview people who buy cars. If you want to learn about diaper buyers, you need to interview people who buy diapers. If you want to learn about beer drinkers, you need to interview beer drinkers. And if you want to learn about likely Republican caucus-goers in Iowa or primary voters in New Hampshire, you should interview likely caucus-goers in Iowa and likely primary voters in New Hampshire.  

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