Likely Voters and Polls

Hi Everyone,

The poll numbers are all over the place these days. Some polls show Bush ahead by 8 points or so. Most other polls show Bush and Kerry tied or at least within the margin of error. There are even some polls in the last week that show Kerry ahead among "registered voters."

This has lead to a kind of "my poll can beat up your poll" argument among prognosticators both amateur and professional. This leads to a series of questions:

1) Are all polls equal? Answer: No.

Some polls are much more carefully done than others. A friend of mine at the University of Miami (Fla) has told me some hair raising tales about what passes for a usable poll for the Miami Herald. He told me he's seen their raw data and its a joke. They just make up the margin error some times. They hire professors from local community colleges to do the polls even though these folks may not have the training, experience or staff to conduct an unbiased poll. My advice would be to very suspicious of any poll done by a newspaper without a national reputation. NYT, WSJ, Washington Post and maybe the LA Times are probably OK but don't read to much into a poll by the Indianapolis Star for example.

Also, some polls are "push polls." In this age of image dominated TV journalism, polls can BE the story. That means that both parties have incentive to show their guy ahead as much as they can. Polling groups with ties to one party or the other will give polls that intentionally push a particular result: For example they'll ask a bunch of questions about corporate corruption, Haliburton, Enron etc and then ask if you have a favorable opinion of Dick Cheney. Or they'll ask a lot of questions about protecting Americans from terrorism and defending "the Homeland" and then ask you if you intend to vote for Bush. Strategic Vision is the most commonly reported poll that has a clear tie to the Republican Party. Their results have differed from independent polls by as much as 10 percentage points - always in Bush's favor.

Finally, there are polls that fiddle with the sample. Polls are presented as "random samples" but they aren't really random. What they are is "normalized" which is a lot different. Polls actually have quotas for Republicans, Democrats, Independents, women, men etc. The recent Time poll that showed Bush ahead by 12 points had 10% more Republicans in their sample than there are registered Republicans nation wide. A number of pollsters criticized this poll for biasing the results.

2) What is a "Likely Voter?" Answer: Depends on the poll.

Usually, pollsters give screening questions about past voting history to determine if a respondent is a likely voter or just a registered voter. But there is little confidence that the screening really identifies people that are going to vote in the next election. Usually Republican candidates do better among likely voters than among registered voters. Here are some demographic characteristics that political scientists have identified with higher voter turnout (note: not a prediction of individual behavior as in the pollsters' "likely voter" terminology):
The higher the age group the higher the turnout.
Turnout is higher among men than women.
Turnout is higher among Whites than non-Whites.
Turnout is higher among higher income brackets.
So what does this mean? Well, it generally means that when turnout is low, the share of the votes cast by older, White, rich men goes up (guess which party they vote for). When turnout is high, the share of the votes cast by this group goes down. Most of the polls for this election say that turnout is going to be unusually high in 2004. Latino, Black, overseas and youth turnout are all expected to be MUCH higher than in the past. This could be interesting because these are all groups that will be more likely to vote for Kerry but will be unlikely to be included in "likely voter" polls. Indeed, overseas voters aren't counted at all. Remember how I said some polls of "registered voters" show Kerry slightly ahead? This could explain that result.

3) Can any one poll tell us anything? Answer: Not really.
You shouldn't look at just one poll and declare that you've learned anything with any precision. You have to dig a little and find out as much detail about as many polls as possible. Look at what kind of voters are supporting each candidate. Look at the trends over time. Check to see if a poll you're looking at is consistently more favorable to one candidate or the other.