The polling in the 2018 election was terrible. In the hotly contested Senate and governor races that played out across the country, 4 out of 10 polls were wrong (i.e., predicted the wrong winner).
And 60 percent of the polls got the final numbers wrong by 3 points or more (even if they picked the right winner).
A more or less 50-50 verdict on their accuracy makes the polls, according to the law of chance, about as likely to pick the winner as random selection.
Now that the ballots are all cast — and mostly counted — it's time to assess which polling firms had it right and which had it wrong. We can also figure out which had the most pronounced Democratic bias and which were more Republican in their skew.
Overall, there were 40 final polls taken in the key statewide races around the country. Thirty of the 40 showed Democrats doing better than they actually performed. Only 10 showed Republicans doing better.
Of the nine major polling firms, eight showed Democrats doing better than they actually did, and only one — Trafalgar — showed Republicans doing better than it turned out.
Overall, the most accurate polling firm was Quinnipiac University, which, on average, overrated Democratic performance by 2.0 percent. Next came Gravis and Emerson College.
The least accurate, and the most biased toward Democrats, were NBC/Marist and, surprisingly, Fox News. NBC overestimated Democratic vote totals by an average of 6.8 percent and Fox News did so by 5 percent.
Here are the rankings of the polling firms by their accuracy and their partisan bias:
Quinnipiac Average Error: Pro-Democrat 2.0
Gavis Average Error: Pro-Democrat 2.5
Trafalgar Average Error: Pro-Republican 2.7
Emerson Average Error: Pro-Democrat 2.8
CNN Average Error: Pro-Democrat 3.0
Harris Average Error: Pro-Democrat 3.5
CBS Average Error: Pro-Democrat 4.0
Fox News Average Error: Pro-Democrat 5.0
NBC/Marist Average Error: Pro-Democrat 6.8
This list was compiled by comparing the final polls by each company in each race with the actual outcome and then averaging their margin of actual error.
It is time for the pollsters to clean up their act and get it right. That the media outlets that publish these polls do not reprimand or punish their contractors for these inaccurate polls simply enables them to continue to get it wrong.
Why are most of the wrong calls in favor of Democrats? Legitimately, Democratic voter turnout is harder to predict than Republican, with so many variables in harder-to-poll groups such as minorities and young people. But, particularly at firms like NBC, the possibility of editorial bias cannot be discounted.
As for why Fox News was almost as pro-Democratic in its bias, it's hard to guess.