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September 30, 2004

Debates II: Instant Polls

As I mentioned in the last post, past history shows that the media’s coverage of presidential debates typically has more impact on voter preference than the debate itself. So, as is often the case, we will not know for sure what impact tonight’s debate has until we get back results from new surveys over the next week. However, if you are reading these words, and you’re a political junkie like me, you just can’t wait until next week. Are the instant polls done by the networks tonight worthy of our attention? My take on that follows on the jump page.

Instant polls done to assess the impact of the debate face two big challenges.

The first was anticipated by this set of questions posed by astute commenter Simka, who asked:
· What about people who work at night when pollsters call?
· What about people who go to school at night?
· What about people who work two jobs?
· What about people who work late?
· What about people who work swing shifts?
· What about people who are traveling? How many Americans are on the road at any given time for work or family

This question identifies one of the biggest sources of non-response (the other being those who simply hang up): At any given time, not everyone is home. Pollsters have to be persistent, and call over multiple nights at different times get to a reasonable number of those not always home. Although the specific procedures vary, most pollsters call at least four times over at least 2-3 evenings. This doesn’t get everyone, but gets close. Without rigorous "call-backs,” the sample will be biased against the people who are often away from home. That is why you rarely see one night polls done nationally.

That problem is greater for a post debate poll since, duh, people at home tonight will be more likely to watch the debate. As a result, most of the surveys done tonight will concentrate on those who actually watched the debate.

The second problem is one of interpretation. More often then not, the actual debate serves to reinforce voters’ preexisting preferences. In other words, all things being equal, Bush supporters will come away more impressed with Bush, Kerry supporters more impressed with Kerry. Thus, if Bush goes into the debates with a five-point margin among those in the sample, and the debate does nothing to change initial preferences, then expect the question that asks who "won” the debate to show a similar five-point margin.

The most sophisticated way to try to measure the impact of the debate itself would be to contact a random sample just before the debate, ask about their vote preference and attitudes toward the candidates, then call back just after the debate, repeat the same questions and ask the respondents to judge each candidate’s performance. Such a design allows the pollster to compare the reactions of pre-debate Kerry supporters to pre-debate Bush supporters and measure whether either candidate gained or lost support among individual respondents.

That is exactly the design used by the ABC News Polling Unit for all four of the presidential and vice-presidential debates in 2000. Here are a few examples of their results: The first debate looked like a dead heat (Gore fell in the polls in the week that followed due to coverage of the debate, but reaction to the debate itself was more favorable). Although slightly more Gore supporters (79%) than Bush supporters (70%) thought their man won, Bush’s support increased by 1 percentage point during the debate. After the second debate, 76% of Bush supporters judged their man the winner vs. 63% of Gore supporters who thought their man won. Bush’ margin grew from 10 to 13 points during the debate. (Press releases for all four of these surveys are still available online here, here, here and here).

Of course, one drawback of ABC’s approach is that, even with respondents waiting by the phone for the second interview, it will take at least an hour or so to complete the calls and tabulate the results. Other respondents might spend time watching the commentary following the debate before doing the interview.

The CBS polling unit tried a different approach four years ago. My sources tell me they will use the same approach tonight. In 2000, CBS conducted a survey online with a company called Knowledge Networks, which maintains a nationally representative "panel” of households that agree to do surveys on the Internet. What makes Knowledge Networks unique is that they recruit members to their panel with traditional random digit dial (RDD) sampling methods, and when a household without Internet access agrees to participate, they provide those households with free access to the Internet via Web TV. So in theory, at least, this approach allows a random sample of all US households.

The advantage of the KN online poll is that every selected respondent receives a pre-debate invitation, so they can log-on and fill out the survey immediately after the conclusion of the race. In 2000, for example, 617 surveys had been completed within 15 minutes of the conclusion of the debate (See the releases from 2000 by CBS, here and here, and by Knowledge Networks. Also, the raw data from these surveys are available to scholars here).

One disadvantage, at least in the way the CBS survey was done four years ago, was that they either did not do a pre-debate interview or did not report the post-debate results that way. Perhaps the design this year will be different.

The bottom line: If you are willing to be patient, the best methodology is the one that ABC News used four years ago, which interviews voters before and after the debate and compares results among pre-debate Kerry supporters and pre-debate Bush supporters.


Related Entries - Debates

Posted by Mark Blumenthal on September 30, 2004 at 02:48 PM in Debates | Permalink

Comments

"The most sophisticated way to try to measure the impact of the debate itself would be to contact a random sample just before the debate, ask about their vote preference and attitudes toward the candidates, then call back just after the debate, repeat the same questions and ask the respondents to judge each candidate’s performance."

If you are trying to measure the impact of the debate nationally, I wonder if this approach is really valid. By asking people to express their vote preferences before the debate, you may be "crystallizing" a preference in the minds of people who might otherwise be inclined to form or change their opinions during the debate. Would it not be preferable to randomly assign the pollees into two groups, one of which is asked for preferences before the debate, the other after? (As an experiment, the first group could also be asked after, using the second group as a control, to see if the experience of being polled before the debate has an effect one's persuadability.)

Posted by: Elliot | Sep 30, 2004 3:33:41 PM

I am no expert, but is it possible that you are neglecting another factor? You talk about how people respond immediately after the debate, and also a few days after the debate, and seem to characterize the latter as being a consequence of TV coverage. (Forgive me if I misunderstood what you were saying.)

But what about word of mouth? I will tell you that I am one of those junkies who will watch the debates, and then obsessively channel surf the various cable news channels to see what their commentators are saying. But all I expect to see are talking points, for the most part. Much more important to me is what I will hear the next few days from my friends and family who may also have watched the debates. Is it not possible that discussion around the water coolers is what really drives the long term reaction to how the candidates perform?

Posted by: Brandon | Sep 30, 2004 3:35:14 PM

From what I've read of past debates, the reaction of those who listened to it on a radio differers greatly from those that watched on TV. Add a few hours of "analysis"(read spin) after the debate or by morning papers, I have to think it would extremely difficult to to find only influenced by the debate, uninfluenced by hype, undecided.

Posted by: jamesbray | Sep 30, 2004 3:52:50 PM

Mr. Blumenthal,

You wrote:

"As I mentioned in the last post, past history shows that the media’s coverage of presidential debates typically has more impact on voter preference than the debate itself. So, as is often the case, we will not know for sure what impact tonight’s debate has until we get back results from new surveys over the next week."

Is this really shown by past history, or is it something that has come to be conventional wisdom based in part on hastily conducted flash polls?

In the aftermath of any event, there is too much of a chance that what a pollster is picking up is a change in who is willing to participate in a survey, rather than a change in the overall views of the populace, in my estimation.

And if the polls that would measure the debate's impact (before the post-debate spin starts to echo around the media chambers) are not reliable, then there would be no way to be sure that the post-debate spin has more of an effect, less of an effect, or none at all.

Gerry

Posted by: Gerry | Sep 30, 2004 5:13:46 PM

Slam dunk for Kerry.

Posted by: S | Sep 30, 2004 11:23:43 PM

lol.

very funny looking at that comment 3 years l8er. :-)

Posted by: z t | Jan 8, 2008 8:15:15 PM

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