Should You Trust The Polls?

General election polling for special elections in 2018 has been remarkably accurate.

It’s election season. A time when the fancy of political prognosticators turns to opinion polling. Polls are one of the only objective measures of how a race is looking before the official votes are cast, but there is always a question of whether polling is reliable.

Especially since Donald Trump’s unexpected victory in 2016, many consider polls unreliable. The truth is that the polls in 2016 weren’t off as far as many think they were. The popular vote corresponded almost exactly to the national polls in which Hillary Clinton led by about two percentage points. At the state level, Trump eked out victories in a number of states where Hillary led in the polls, but polling in most of those states showed a very close race. Wisconsin, where polling showed Hillary up by about eight points, is the exception. Data from the American Association for Public Opinion Research shows that much of the error was due to a final-week surge after James Comey released his letter to Congress on Oct. 28, 2016.

As I have written before, polls should neither be believed absolutely nor totally discarded. The best strategy is to take each individual poll with a grain of salt. Rather than focusing on a single poll, look for trends. This is easy to do with sites such as Real Clear Politics and FiveThirtyEight that provide comprehensive lists of polls as well as averaging their results. Another good strategy is to discard outliers, single polls that show a radically different result from the rest.

The best way to judge the accuracy of polls is to compare them to the final election results. Since polls are snapshots that record a moment in time, rather than forecasts, this can be done by looking at the polls taken just before the election. Fortunately, RCP and FiveThirtyEight both keep their polling data posted for past elections.

If we compare polling for the four special elections held so far this year with the actual election results, this is what we find:

Pennsylvania’s 18th district was the first special election held this year. It pitted Democrat Conor Lamb against Republican Rick Saccone for the seat of Tim Murphy, a Republican who resigned due to a sex scandal. RCP showed Lamb leading by two to four points in two of the last three polls, giving him an average advantage of two points. When the results were in, Lamb won by 0.4 points.

Next, Hiral Tipimeni (D) and Debbie Lesko (R) vied for the seat of Trent Franks, a Republican who resigned after being accused of sexual harassment for asking to impregnate female staffers. For this race in Arizona’s sixth district, RCP shows two polls. Lesko led in both by an average of eight points. On Election Day, Lesko won by 5.2 points. The 2.8-point difference is the largest error of the three elections.

In the third special election, the race for Texas’ 27th district, there seem have been no public polls. This is not surprising since the district is reliably Republican and was carried by Donald Trump by almost 20 points.

The fourth election was in Ohio’s 12th district where Republican Pat Tiberi resigned to lead the American Business Roundtable. Democrat Danny O’Connor and Republican Troy Balderson ran to fill the seat in this closely watched race. Polling in the race was mixed, especially in the final days. The last two polls showed each candidate up by one point and the RCP average was a tie. Balderson won by 0.8 points.

While polls aren’t expected to be exact or forecast the exact outcome on Election Day, special election polling in 2018 has been pretty good. Over three separate races, the average error for the average of polls was only 1.7 percentage points. Considering that the polls in some races were taken weeks before the election and late-breaking events, such as President Trump’s visit to Ohio three days before the election, can cause voters to change their minds, the results are remarkably accurate.

Don’t assume that every poll that you see is gospel, but if you want an idea of how elections are going to play out, there is no substitute for a close look at the polls. The bottom line is that if candidates didn’t think polls were valuable tools, they wouldn’t pay for them.

For more information on how to skeptically read polls,read this earlier article from The Resurgent.

Comments
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cynicalnerd
cynicalnerd

For me to separate a poll from the noise and make a judgement on whether to trust it or not requires me to know three things about the poll (and the outfit who ran it).

  1. How was the survey ran and who were the respondents. Online like a Surveymonkey poll? Trash. Registered voters? Dicey. Human pollsters targeting Landline and Cellular phones-- polling several thousand likely voters who participated in the last four election cycles? You have the gold standard. (And far and away the most expensive)

  2. What's the R-D-I sampling rate spread and margin of error? (Is that RDI representative of the area? What level of confidence do they ascribe to their polling results?)

  3. The polling outfit's history--How long have they been in the business and how accurate and precise they have been when comparing their polls to the actual election results?

Leftshot
Leftshot

You are comparing polls 5 days out from an election to the election results. We’re not 5 days out. We have no such polls for this election. We’re one month out. Compare the actual results from past elections to the poll numbers one month out, two months out, and 90 days out and you’ll see a very different story.

ekay
ekay

I know a number of people who tell pollsters the opposite of how they are going to vote just because they hate polling. I don't have any idea how many people do this, but I believe their could be a significant number who do not tell pollsters the truth of how they will vote.

NWRED
NWRED

General election polling for special elections? They are two types of elections.. A special election can be one day by itself, a way to concentrate forces.. Money will be pinpointed to that election. People can be brought in for rallies. The question, are you registered to vote should be asked..

With voter regulations being lax in some areas, we don't know if fraud has been committed or not.

Polls can be done by area or zip codes. Democrats seem to be more concentrated in large cities. Do the pollsters call both land lines and cell phones.

How many of those polled refuse to .answer.? With more violence occurring, will people keep opinions to themselves