In the next couple of weeks, pollsters warn us, we may well see the media polls on the presidential election take some wild turns. ABC's Gary Langer predicts the "convention bounce" could cause candidate support to "spike"—"sometimes in an election-changing way." Gallup's Frank Newport seems downright giddy about the next two weeks: "What a fantastic time we have ahead of us! The presidential election process is about to move from stagnating/static to exciting and extremely fast moving."
Yet, when we look at all of the polls, especially those of Gallup and ABC, we see reports that suggest virtually all voters have already made up their minds. How can such a decided electorate be the source of what is expected to be major fluctuations in the polling results?
The answer is that media pollsters approach pre-election polling from what might best be termed a schizophrenic position. On the one hand, they want early poll results that are "meaningful" enough to be published in the news. On the other hand, they know that many people have not yet begun to think about the presidential race, and any views that such voters might express at this stage of the campaign, about what they would do in November, would not be reliable predictors of how they will actually vote.
Indeed, if pollsters told us the truth about the electorate, they would have to report that early on in the campaign, a large segment of the electorate, perhaps as much as 40 percent or so, had not yet begun to pay attention to the presidential contest. But that's not interesting news. Who cares if Obama leads McCain by 5 percentage points, when eight times that number of voters are still undecided?
Pollsters get around this technical detail by asking a forced-choice hypothetical question: which candidates people would vote for "if the election were held today." Should any respondents have the temerity to admit they don't know, pollsters pressure respondents to say whom they "lean" toward, thus producing what appears to be a fully decided electorate. Using that format, for example, Gallup routinely reports 95 percent of voters already decided, ABC says 98 percent, while CNN is the extreme at 100 percent.
The problem is that this hypothetical situation does not represent the actual electorate. Some respondents in poll samples, of course, have made their decisions, and their responses are presumably an accurate picture of the voters at large who have also made up their minds. But the undecided voters in the sample are pressured into giving a response, and once that happens, they no longer represent the undecided voters at large, who have not been pressured.
This contamination of samples cannot be stressed too much. As we all know, in each poll, interviewers speak with only a small sample of voters nationwide, typically about 1,000 or so, and these voters are supposed to represent the larger population of some 200 million voters. In principle, despite the amazement of many nonstatisticians, such a small sample, if chosen correctly, is capable of representing the larger population within a fairly small margin of error. But if we give information to these samples of voters that we do not give to the general electorate or subject these samples of voters to pressure that the general electorate does not experience, then the samples no longer represent the larger population.
And that's the situation with most media poll samples these days. The samples themselves are typically chosen with due scientific precision. However, pollsters pressure all respondents to come up with a presidential choice, even though many have not given the election much thought. Typically, respondents will play the polling game and give an answer about whom they would support "if the election were held today," but for undecided voters, that doesn't mean they actually intend to vote for that candidate. Indeed, if pollsters would allow the respondents their true choice, many would admit they simply don't know yet. Instead, they agree to the pollsters' demand and come up with a meaningless answer.