Political science tells us Hillary Clinton will win the election—the poll numbers are so clearly in her favor. As of this moment, the authoritative FiveThirtyEight “polls only” forecast says Clinton’s chance of beating Trump is 86.6 percent. But polling is an inexact science, and a lot of pundits are asking: Could the polls be wrong this time?
The first problem they point to is that some Trump voters might be lying to the pollsters. “How Many People Support Trump but Don’t Want to Admit It?” Thomas Edsall asked in a recent op-ed. Some voters don’t want to tell a live interviewer that they back a candidate who has been so offensive and outrageous. The pollsters call this “social desirability bias”—“the desire of respondents to avoid embarrassment” in speaking with interviewers on the phone. But on November 8, in the privacy of the voting booth, they will cast their secret ballot for the Republican.
It’s happened before—in California, where I live, we call it “the Bradley Effect.” Tom Bradley, the first black mayor of LA, ran for governor in 1982, and all the polls said he would win—but on election day he lost. White voters broke with Bradley in far higher numbers than polling predicted, and many at the time wondered if it was because he was black. This year we wonder how many men will refuse to vote for Hillary because she’s a woman. They know they’re not supposed to say it, but that won’t stop them from doing it.
The second problem is that the pollsters’ standard criteria for “likely voters” may not work this year. If you are in the polling business, it’s not hard to call people and ask whom they plan to vote for. The hard part is deciding whether to count them as “likely voters”—because more than 40 percent of Americans eligible to vote have not cast a ballot in the last two presidential elections. So all pollsters rank the people they poll on the likelihood of their voting.
On this count the 2012 election was a nightmare for the venerable Gallup poll: They predicted Romney would beat Obama. In their mea culpa afterward they said their number one error was “misidentification of likely voters.” A Pew Research study this year declared that “incorrect forecasts about who will vote . . . may be the most serious” problem facing pollsters. Gallup in 2012 missed Obama supporters because they were ranked “not likely” to vote; pollsters worry the same thing might happen this year with Trump supporters.