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An error margin of as much as two or three percentage points is routinely assumed as a hazard of the pollster's trade—but that could hardly account for the startling discrepancies in last week's results. All three pollsters used basically the same techniques, although they often differ in their philosophies of interpretation. Gallup, for example, believes that "our job begins and ends with the reporting of facts." Harris argues that survey results are meaningful only if they are digested and interpreted. Each pollster has his own methods. Harris likes to reinterview some one he has already talked with, figuring that he can thus detect changes in sentiment over periods of time. Gallup, on the other hand, argues that a second interview makes a voter selfconscious, so that he gives a less accurate reflection of public sentiment.
Sheer Volatility. Most pollsters agree that a sampling of something like 1,500 people yields a fairly comprehensive picture of national trends and opinions. For last week's sampling, Gallup used 1,156 interviews gathered from throughout the country, Harris 1,346 and Crossley 1,976. All but 219 of Harris' samplings were reinterviews.
The sheer volatility of voter sentiment this year probably contributed to the wide differences in the pollsters' findings. Though the primaries were over, some of the same factors still applied: a plethora of candidates, no established party tickets, and moiling confusion in both parties over the issues. Despite the pollsters' fatiloquent accuracy in past years, they have stumbled often in the past six months. Almost all, for example, have consistently underestimated Eugene McCarthy's considerable strength. Harris and Gallup have frequently differed in their preference surveys, though never so widely as in the preconvention week.
If anything, last week's consensus statement simply made matters worse. In persuading Gallup to endorse the apologia, Harris may have widened the trade's credibility gap to the dimensions of 1948, when virtually every opinion sampling was ushering New York's Thomas E. Dewey into the White House. Twenty years later, the memory of that year sends shudders down the spines of all pollsters. One pollster called last week's results "a fiasco." Another, Burns Roper, observed: "If this statement of 'open lead' for Rockefeller is construed by readers as being designed to influence the outcome of the Republican Convention, it will be most unfortunate, both for the political process and for the public-opinion polling profession."
The pollsters' main problem—which led in part to last week's statement—is that politicians and the press are constantly exaggerating the importance of the polls. Many analysts, including pollsters, are beginning to wonder whether "racehorse" surveys taken in the heated confusion of a presidential campaign are worthwhile, since the temperature of the electorate can vary by half a dozen points from one week to the next.