Pollsters using the voter files know the party registration of the intended respondent before they place the call. At the same time, 6 percent of registered Democrats identified as Republicans, while just 3 percent of registered Republicans now identified as Democrats.The polls that rely on voter files can help in another way: The pollster can tell whether there was a difference between Republicans and Democrats in their willingness to complete interviews. The polls discussed here do weight by education, but some other kind of bias can never be ruled out. The errors are so large that it’s hard to trust their results on other measures. In addition to writing for The Times, he has discussed politics on CNN, MSNBC, C-SPAN, and NPR, and at major colleges and universities.
But to critics, the partisan makeup of most public polls is self-evidently out of step with a closely divided country.There are many reasons the polls might ultimately be wrong in November, as many state polls were four years ago, but there’s no serious evidence that the polls are systematically missing Republican voters. In 2016, the failure of many state pollsters to weight by education wound up biasing surveys against Democrats: They might have had the right number of Democrats or Republicans, but too many of each had a college degree. And if Republicans are just as likely to respond to surveys as Democrats, there’s little reason to believe that they’re vastly underrepresented in political surveys.It is hard to convey the surprising and complete irrelevance of partisanship in whether someone responded to the Times/Siena survey. Even if the exit polls were more accurate on these demographics, they would still be just a snapshot of the electorate four years ago. It’s just what their results show.Of course, those results could still be wrong. This doesn’t prove that more voters identify as Democrats today, but the Democratic advantage in registration and recent primary participation nonetheless offers evidence consistent with the basic proposition that Democrats outnumber Republicans, and probably significantly.Using this data, we found that self-identified Democrats outnumbered Republicans by eight percentage points in the Times/Siena national poll (the unrounded figures are Democrats 34.5 percent to 26.4 percent for Republicans). The Trump campaign pollster John McLaughlin, for instance, cited the 2016 exit poll results to argue that public polls understate the number of Republicans by a clear margin. He covers elections, polling and demographics. Before joining The Times in 2013, Mr. Cohn worked as a staff writer for The New Republic and as a research associate at The Henry L. Stimson Center. If it turned out that Democrats were far likelier to respond to telephone surveys than Republicans, the public polls could be systematically biased — and the critics would be vindicated at the ballot box.Ultimately, there’s no way to be absolutely sure that the polls include the right number of self-identified Democrats or Republicans. In the last Times/Siena polls of six battleground states, for instance, respondents who voted in the 2016 election said they voted for Mr. Trump over Hillary Clinton by a margin of 2.5 points, which was even more than Mr. Trump’s actual margin of victory.Mr. This might simply mean there are more Democrats than Republicans. Nate Silver’s FiveThirtyEight uses statistical analysis — hard numbers — to tell compelling stories about elections, politics, sports, science, economics and lifestyle. By Nate Cohn Voting in Florida’s primary in March. When checked against census or voter file data, the exit polls are demonstrably inaccurate on many variables, like age and education. Over all, telephone calls to registered Republicans or those who participated in a recent Republican primary were about 12 percent likelier to yield a completed interview than calls to Democrats were. Even so, it is hard to reconcile these data with the idea that Republicans, as a group, are systematically understated.And there are reasons to doubt that Mr. Trump’s voters are being understated. We know that registered Democrats outnumber registered Republicans in Florida by a few points, even if we don’t know whether those same voters would identify as Democrats or Republicans today.Pollsters can take advantage of this if they use voter registration files, a large data set of every registered voter. Arguably, they offer a picture even worse for Republicans.Voter-file-based data lends credibility to polls showing a lopsided Democratic advantage in other ways. If Democrats were far likelier than Republicans to respond to telephone surveys, then polls could be systematically biased. As a result, it’s easy to tell whether members of one party or another were more or less likely to respond to a survey.If registered Democrats were likelier to respond than registered Republicans, it would undermine a core assumption of most public pollsters.
This seemingly noteworthy difference can be explained by well-known demographic biases in polling: Older, rural and white voters are likelier than young, urban and nonwhite voters to respond to surveys. By contrast, the CNN/SSRS poll Mr. McLaughlin criticized found that Democrats outnumbered Republicans by seven points among the adult population, with Republicans at just 25 percent of the sample.But few serious pollsters rely on the exit polls to determine the demographic or political makeup of their samples, with good reason.
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