The Hill

By Reid Wilson – 09/01/16 06:00 AM EDT

Pollsters are debating whether Donald Trump’s “silent majority” of voters exists, and are scrambling to make sure that their surveys reflect the opinions of voters who might not ordinarily be included in opinion polls.

Democratic and Republican pollsters alike are determined to get their predictions for the 2016 elections right in the wake of a series of high-profile missed calls.

Partisan claims of skewed results have also escalated, with Trump and his unconventional claim asserting that polls aren’t capturing the Republican presidential nominee’s true support.

Trump claims his campaign will turn out millions of new or irregular voters in November, some of whom will be voting for the first time.

Some pollsters acknowledge the race presents some new challenges.

“We know some people who are traditionally seen as unlikely voters are going to vote,” said Nick Gourevitch, a partner at Global Strategy Group, which polls for Democratic candidates. “You need to take those people into account, and if you just lop those people off, you’re going to miss something.”

Modern public opinion polling is as much art as science.

The science comes in measuring the attitudes of the American electorate, and key demographic groups, in a statistically valid way. The art comes in defining just what that electorate will look like, and how much of a percentage of the electorate key demographic groups will make up.

Variations in those models can change the outcome of a poll.

In 2012, Republican polling firms underestimated the number of minority voters who would show up to vote in November. That left a number of GOP pollsters anticipating a win for their presidential nominee, Mitt Romney. Democrats and most non-partisan pollsters predicted a different model, one in which minorities would make up a greater share of the electorate. Those pollsters were closer to the electorate’s actual makeup, and President Obama won reelection.

“At some level, [voter models are] based on a hunch about the future and how it will resemble the past,” said Ann Selzer, a nonpartisan pollster who conducts surveys for Bloomberg, the Des Moines Register and the Indianapolis Star. “The best predictor of future behavior is past behavior, until there is change.”

Pollsters typically ask a battery of screening questions designed to test whether a respondent is likely to vote in November. Those who are likely to vote make it into the poll’s sample; those who say they are unlikely to vote get a polite thank you and goodbye. The pollster’s goal is to survey a sample that most accurately reflects what the general electorate will look like.

After Romney’s defeat, a postmortem conducted by the Republican National Committee found many GOP pollsters were concerned that the rising use of cellphones and the decreasing willingness of Americans to participate in half-hour long surveys were harming their ability to predict accurate turnout models.

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