The Perils of Polling in Low-turnout Primaries

Recently Energy Independent Vermont commissioned a poll conducted by Fairbank, Maslin, Maullin, Metz, and Associates (FM3), a public opinion research group that works primarily with Democratic candidates and a wide array of governments, non-profits, and corporations. The poll interviewed 600 registered Vermont voters, and although little additional information about the methodology was published, the report claimed to represent “likely voters” defined by those “who said they are likely to vote” (from Polhamus, Mike. “Poll finds support for carbon tax, other climate change steps.” VTDigger. Accessed online on July 12, 2016). Self-reported likelihood to vote is a notoriously biased number, even in the best of elections; this is what pollsters call social desirability bias.

The poll reported 65 percent of respondents saying that they are likely to vote in the state primary; the voter turnout in the last gubernatorial primary election without an incumbent (2010) was only 24 percent, and in 2014 the turnout was only 9 percent. Given prior elections, 65 percent is an unrealistic projection for state primary turnout.

While I admire FM3’s attempt to poll in these important primaries, I contend that a much larger sample is necessary. It may be counter-intuitive to some, but polling is much easier in large populations than in small populations. What is most difficult about the projections of the population voting in primaries is that the parameters of these populations are generally unknown. We do not have exit poll data to tell us about the general patterns of state primary voters. The best indicator we have for whether or not someone will vote in the state primary is one’s past voting history, which can be obtained from voting records. Past behavior is the best predictor of future behavior.

When the voting population is small, the danger of using past voting behavior is that mobilization of just a small number of new voters—voters not picked up in a sample frame including only past voters—can make a large impact. In other words, a strong get-out-the-vote (GOTV) movement can overcome name recognition, advertising, and direct mail disadvantages.

The FM3 poll may be right on target, but it is more likely that the respondents in the late June poll will not look like the voting population in the August 9th election because, unless this is a fortunately unrepresentative sample of registered voters, most of these respondents are not likely to vote in the state primary.