Ask the Expert: Can we trust election polling?

October 20, 2020 - Liz Schondelmayer

In the months leading up to this year’s historic presidential election, news headlines have consistently highlighted movement in national polls: who's up, who's down and who's winning in each state. For many voters, these polls can be confusing, and a challenge to interpret and trust. Corwin Smidt, associate professor and chair of the Department of Political Science, explains how poll data is collected, how to interpret it and why polling data shouldn’t dictate public opinion when voters cast their ballots.

What is the actual process for collecting public opinion poll data ahead of the election?

“It used to be that pollsters used a fairly uniform method for gathering data, which was predominantly done via landlines and mail-ins. One common practice was called ‘random digit dialing,’ in which pollsters would just select a phone number from within a certain state and call.

“Today, there's not one single process for polling. Surveyors will use cell phones, landlines, the internet, the mail ... there isn't one standard practice. 

“Oftentimes, pollsters will develop an interview, randomly select a group of people to call, gather data on their opinions and then project those opinions onto what they think the voter populations look like in the state. Sometimes, instead of selecting surveyors will also target specific people from certain voter registration lists or who match a specific profile.”

How can voters tell if a specific poll is reliable? 

“It's important to understand that each single poll is a snapshot of a much larger picture, and no poll is perfect. Polls can have a margin of error of 4 to 5%, meaning if a candidate is up by "10 points," they really could only be leading by 4 or 5%, which still makes for a very close race. 

“When polls reference ‘points,’ it simply means the percentage points a certain candidate is leading or trailing by. For example, if Candidate A is pulling 55% of the vote based on the polling data and Candidate B has 45%, Candidate A would have a lead of 10 points. 

“When considering a poll's reliability, it's more important to look at polls as an aggregate rather than looking at just one poll at a time. If you want to know if a specific poll is meaningful, look at previous polls of the same demographic, or look at three or four polls together.

“It's also important to note that when polls are conducted, they often ask questions about how people would vote ‘if the election was held today.’ But the election has been going on for a year - people are already voting, and are going to be voting up until election day. So, that could skew results as well.”

Should voters consider polls when deciding which candidate to support?

“My rule of thumb is that when you are casting your ballot, you should always vote based on what you think is the best expression of who you are. Voting strategically based off of the polls is counterintuitive, because you're more likely to get struck by lightning twice than have your personal vote be the one that decides an election. Thus, vote for the candidate you believe in and the outcome you are personally hoping for. 

“For most people, the reason we watch the polls so closely is because we're scared or uncertain about the future. So, if you see the polls and are scared that your candidate might lose, that's a good reason to go volunteer. Or, if you're thinking your candidate might win, that's a good reason to invest your time and energy into a different candidate who could use some support. Let the polls inform your campaign involvement, but not the actual casting of your ballot.”