Understanding Gallup's Likely Voter Procedures for Presidential Elections

Since 1950, Gallup has used likely voter models to identify Americans who are most likely to vote in upcoming presidential elections. These procedures address the need to winnow down national adult or registered voter surveys to a subset of respondents who are most representative of the likely voter electorate. Many more people say they will vote than actually do, so it is not sufficient to simply ask people whether they will vote.

Gallup's likely voter procedures involve asking poll respondents a variety of questions about their interest in the coming election, their past voting behavior, and their intention to vote in the coming election (see the exact question wording in the "Question Wording" section). Gallup analysts have developed and validated these questions over the years and have modified them as necessary to take into account new information and changes in the ways in which the voting process takes place.

Gallup gives respondents one point for each question they answer in a way consistent with voting (the scoring scheme is detailed in subsequent paragraphs), resulting in overall likelihood of voting scores ranging from zero to seven. Gallup has then used various procedures to set a threshold for the pool of likely voters. The validity of setting a threshold based on a specific estimated turnout among the voting age population (VAP) or voter eligible population (VEP) is less clear than it was in the past, particularly given real-world changes in voting, such as early voting and decreases in survey participation rates. For the 2008 and 2012 elections, Gallup considered respondents with the highest scores (six or seven) to be likely voters.

Questions Gallup Uses in Its Presidential Election Likely Voter Model

For the seven questions that make up the likely voter scale, respondents receive one point on the likely voter scale for each question to which they give the response listed in parentheses (with a maximum of seven points possible). See the full question wording for each question in the "Question Wording" section.

1. Thought given to election (quite a lot, some)
2. Know where people in neighborhood go to vote (yes)
3. Voted in election precinct before (yes)
4. How often vote (always, nearly always)
5. Plan to vote in 2012 election (yes)
6. Likelihood of voting on a 10-point scale (7-10)
7. Voted in last presidential election (yes)

Gallup also measures the increasing trend of people voting before Election Day by asking people when they plan to vote and then incorporates this information when determining if people are likely to vote.

For the raw scores, Gallup makes the following adjustments:

• Respondents who are not registered to vote receive a score of zero.
• Respondents who do not say they plan to vote (see item No. 5) receive a score of zero.
• Respondents who report that they already voted receive a score of 7.
• Given the rise in voting by mail, respondents who say they do not know where people in their local district go to vote receive credit for that question if they say they plan to vote before Election Day and say they have voted in their precinct in person or by mail in past elections.
• Gallup adjusts younger respondents' scores to account for their ineligibility to vote in some or all past elections. In other words, even though the model identifies voters based on past voting history, Gallup does not penalize younger voters for not being of voting age in past election years.
  
  
• • If aged 18 to 19, Gallup converts their scores as follows: 1=2, 2=4, 3=5, 4=7
  • If aged 20 to 21, Gallup converts their scores as follows: 1=1, 2=3, 3=4, 4=6, 5=7

Question Wordings

1. How much thought have you given to the upcoming election for president -- quite a lot, some, or only a little?

1. Quite a lot
2. Some
3. Only a little
4. None (vol.)
5. Don't know
6. Refused

2. Do you happen to know where people who live in your neighborhood go to vote?

1. Yes, any response given
2. No
3. Don't know
4. Refused

3. Have you ever voted either in person or by mail in your precinct or election district?

1. Yes, any response given
2. No
3. Don't know
4. Refused

4. How often would you say you vote -- always, nearly always, part of the time, or seldom?

1. Always
2. Nearly always
3. Part of the time
4. Seldom
5. Never (vol.)
6. Don't know
7. Refused

5. Do you, yourself, plan to vote in the election this November, or not?

1. Yes
2. No
3. Don't know
4. Refused

6. I'd like you to rate your chances of voting in November's election for president on a scale of 1 to 10. If 1 represents someone who definitely will not vote and 10 represents someone who definitely will vote, where on this scale of 1 to 10 would you place yourself?

1. Definitely will NOT vote
2. 02
3. 03
4. 04
5. 05
6. 06
7. 07
8. 08
9. 09
10. Definitely WILL vote
11. Don't know
12. Refused

7. In the election for president in November 2012, did things come up that kept you from voting, or did you happen to vote?

1. Yes, voted
2. No, did not vote
3. Don't know
4. Refused

Note: (vol.) = volunteered response

Early voting question:

Which of the following applies to you? (Read 1-3)

1. You have already voted in this year's election, either by absentee ballot or early voting opportunities in your state
2. You plan to vote before Election Day, either by absentee ballot or early voting opportunities in your state, OR
3. You plan to vote on Election Day itself
4. Don't know
5. Refused