How Do Polls and Exit Polls Handle Early Voting?

The most common questions I have been getting via email the last two weeks are about early voting. Specifically, how are pollsters dealing with early voting on the pre-election polls we report and how will exit pollsters deal with the early and absentee voters that do not show up at polling places on Election Day?

The answer to the first question is that just about every pollster is either modifying their screen questions or asking additional questions to allow and attempt to identify early voters. Here is a sampling of how some of the national pollsters ask about early voting.

  • CBS News/New York Times: How likely is it that you will vote in the 2008 election for President this November - would you say you will definitely vote, probably vote, probably not vote, or definitely not vote in the election for President, or have you already voted?
  • Fox News/Opinion Dynamics: When do you plan to vote in the presidential election -- did you already vote, do you plan to vote early -- meaning sometime before Election Day, or will  you vote on Election Day?
  • Gallup/USA Today: Which of the following applies to you - you have already voted in this year's election, either by absentee ballot or early voting opportunities in your state, you plan to vote before Election Day, either by absentee ballot or early voting opportunities in your state, or you plan to vote on Election Day itself?
  • GWU/Battleground: What is the likelihood of your voting in the elections to be held in November -- are you extremely likely, very likely, somewhat likely, or not very likely at all to vote? (Accepts "already voted" as a volunteered response).
  • Pew Research Center: Do you plan to vote in the presidential election, have you ALREADY voted, or don't you plan to vote?

While verbatim questionnaires are harder to come by for state level polling, the questions are presumably similar. It is worth keeping in mind that, as with self-reported measure of voting, these questions may overstate the degree of early voting as some respondents will claim to have voted when they have not.

But key point that some seem to miss: None of the pre-election polls (or at least none that I know of) are excluding early voters from their samples. The totals reported include both early voters and those still considered "likely" to vote next week, so no, we do not have to try to somehow account for early voting in interpreting the poll numbers posted and estimated on Pollster.com or other poll aggregation sites.

What about the exit polls? The exit pollsters have, for several elections conducted telephone surveys the week before the election among those who have already voted in states with a rate of early voting they consider significant enough to affect the results. On election night, they combine the early voting telephone survey results with interviews conducted at polling places (except for Oregon, where all voters cast ballots by mail). In 2004 , they did telephone surveys of early voters in 12 states: Arizona, California, Colorado, Florida, Iowa, Michigan, Nevada, New Mexico, North Carolina, Tennessee, Texas, Washington and nationally (for their national exit poll).

A few days ago, Kate Phillips of the New York Times reported these helpful details on this year's plans, which will apparently include six more states:

Joe Lenski, the executive vice president of Edison Media Research, which along with Mitofsky International, conducts the exit polls for a consortium of news organizations, said the group has already expanded its plans for telephone surveys of early voters to 18 this year from a dozen states in 2004. The states are selected based on their competitiveness in the election and on their high rates of voters who cast ballots before Election Day.

[...]

Beginning this week through the weekend, Edison/Mitofsky will conduct random phone surveys in those 18 states, asking detailed questions of people who actually say they voted early. Mr. Lenski wouldn't release the list of all 18 states, but it's pretty apparent that California, Colorado, Nevada, Florida, North Carolina, Georgia and New Mexico will be among the targets.

We're told that Pennsylvania and Virginia - still considered battleground states - won't be among those surveyed before Election Day because those states' rates of early voting/absentee voting are traditionally lower than others.

One caveat: This survey is conducted among landline telephone users only, despite pollsters' growing practice of capturing cellphone users as well. Mr. Lenski and others asserted that shouldn't make much of a difference, because recent research indicates that there aren't huge differences on issues between landline and cellphone respondents. But the Pew Research Center has detected a slight difference when it comes to horse-race figures, suggesting that cellphone surveys capture more younger voters who heavily favor Senator Barack Obama. On Election Day, exit poll interviews will include questions about cells.

It is probably worth adding that exit poll interviews are just one component of the data that the networks use to estimate the election result and (ultimately) weight the exit poll tabulations we will see on Election Night. They will be looking at samples of actual returns very shortly after the polls close. Some states will make separate tabulations of early voting available immediately. Needless to say, the "decision desk" analysts will consider the potential impact of early voting in their projections.

Phillips' article has much more on the early voting phenomenon. It's worth reading in full.

[An earlier version of this post mangled the Fox News early vote questions -- apologies for the error].