I’m going to preface this by saying I am writing this on the Friday before the election. I don’t know if the polls are going to be wrong on Tuesday, but I want to be proactive. After 2016, I learned that there were people who didn’t understand the uncertainty about polling and election models. I also watched the attacks on many of the leaders of my field for their alleged partisan bias that caused them to underestimate Trump. I can’t speak for other people political motivations, but the models are polls built using sound statistically methodology.
The fact is that polls have uncertainty. They can be wrong and sometimes will be wrong for a few reasons. Polls have huge nonresponse rates, for example in the New York Times live polls you can see that usually only 2-4% of the people called answer. And since those that don’t answer can be different than those who answer the polls the polls can be biased based on nonresponse. Nonresponse could be easily fixed if more people answered their political calls or completed online surveys that they are chosen to participate.
Secondly, the structure of polls relies on assuming that individual people favor the candidates at similar rates and that one voter is not affected by other voters. This assumption is for convenience because if you don’t have this assumption is practically impossible to estimate a margin of error. So polls usually make this assumption, which that an interpretation of 95% of all polls contain the real result in the margin of error is an overestimation of the certainty.
A heuristic I like to use is doubling the margin of error because that roughly represents the true error of polls. One thing you will notice in this election is that a lot of the polls are close. This means that we can not be sure who runs in quite a lot of races. In the Senate, about four races (ND, NV, MO, FL) are to close for the polls to predict the winner with a high degree of certainty.
I expect that my model will have an average error of about 3-4 points. Some of the error is going to come from bad estimates in noncompetitive races with limited polling, but in the competitive races, I should be off (hopefully) by 2-3 points. Which means it would not be surprising for me to incorrectly call 2 to 3 races, but on the other hand I could be completely right or miss four races and not be surprised.
Election prediction is an inexact science, and while pollsters try our best, since elections have uncertainty, we will be wrong sometimes. But for me at least, I predict because I love the challenge and trying to make sense of a complicated event. I will be wrong sometimes, but when I’m right its a great feeling to have defied the uncertainty that makes my job difficult.
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