With only three days before what may be one of America’s most consequential elections, what do the polls say about the most competitive races and can we trust them? [NOTE: FH updated poll info below on Nov 5, one day before election.]
Voters felt that most 2016 presidential election polls were inaccurate. President Trump labeled them ‘fake polls’ and even blamed them for GOP voter suppression: “They put out these horrible polls, and then they hope that everyone’s going to say, ‘Hey, look, I like Trump, but he’s got no chance of winning.’ Suppression, it should be illegal actually. You want to check these pollsters, where they’re coming from, they knew.”
So we at FH searched for a way to hold pollsters accountable, and found that FiveThirtyEight, a website that focuses on opinion poll analysis, politics, economics, and sports blogging, had already done it!
FiveThirtyEight has evaluated pollster performance from the presidential election on November 8, 2016 until today. To do them justice, we include FiveThirtyEight’s exact explanation of how they performed their evaluation:
FiveThirtyEight has rated pollster performance over a large sample of elections — rather than placing a disproportionate amount of emphasis on one or two high-profile races. So which pollsters have been most accurate in recent elections? Because some races are easier to poll than others, we created a statistic called Advanced Plus-Minus to evaluate pollster performance. It compares a poll’s accuracy to other polls of the same races and the same types of election. Advanced Plus-Minus also adjusts for a poll’s sample size and when the poll was conducted. (For a complete description, see here; we haven’t made any changes to our methodology this year.) Negative plus-minus scores are good and indicate that the pollster has had less error than other pollsters in similar types of races. The table below contains Advanced Plus-Minus scores for the most prolific pollsters — those for whom we have at least 10 polls in our database for elections from Nov. 8, 2016 onward. These polls cover the 2016 general election along with any polling in special elections or gubernatorial elections since 2016.
Based on FiveThirtyEight’s method of evaluating the accuracy of pollsters, where a more negative Advanced Plus-Minus score is better, which pollsters were the best and worst? The top three pollsters have been Monmouth University, Emerson College and Sienna College, which had the best Advanced Plus-Minus scores. The worst pollsters have been Google Surveys, University of New Hampshire and SurveyMonkey, which had the worst Advanced Plus-Minus scores.
In an attempt to improve the accuracy of current polls for key races, we created new predictions by:
- Picking the ten most competitive House toss-up races and the top 10 Senate and Governor races
- Selecting the latest poll (per RealClearPolitics) by the best pollster (per FiveThirtyEight) for those races
- Adjusting the selected poll by the bias calculation in the far right column of FiveThirtyEight’s chart above
And here are FH’s bias adjusted poll prediction results:
The effect of utilizing a bias calculation is varied between the three race categories:
- House – Flipped four (4) wins from DEM to GOP and three (3) ties to GOP wins.
- Senate – No effect.
- Governor – Flipped one (1) win from DEM to GOP.
Our conclusion is that the general consensuses for Senate and Governor races as reflected in the polls will probably be born out in the election, however, control of the House may turn out differently (or at least closer) than the ‘experts’ predict.
FiveThirtyEight’s conclusion is that the Democrats need a systemic polling error to win the Senate and the Republicans need the same to win the House. It happened once before, on Nov 8, 2016, so it could happen again.
You will note that we left open a column at the far right of each chart for an update with actual election results. We look forward to assessing the accuracy of the polls, FiveThirtyEight’s pollster assessment, and our bias adjusted predictions.
VOTE !!!!!!!!!!!!!!!!!!!!