Felson, Marcus

Sudman, Seymour

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Faculty Working PapersTHE ACCURACY OF PRESIDENTIALPREFERENCE PRIMARY POLLSMarcus Felcon and Seymour Sudmtm#196College of Commerce and Business AdministrationUniversity of Illinois at Urbana-ChampaignFACULTY WORKING PAPERSCollege of Commerce and Business AdministrationUniversity of Illinois at Urbana-ChampaignJuly 30, 1974THE ACCURACY OF PRESIDENTIALPREFERENCE PRIMARY POLLSMarcus Felson and Seymour Sudmtui#196Digitized by the Internet Archivein 2012 with funding fromUniversity of Illinois Urbana-Champaignhttp://www.archive.org/details/accuracyofpresid196felsTHE ACCURACY OF PRESIDENTIALPREFERENCE PRIMARY POLLSbyMarcus Felson and Seymour Sudman** Marcus Felson is Assistant Professor of Sociology and Seymour Sudmanis Professor of Business Administration and Sociology, University of Illinoisat Urbana-Chanpaign.THE ACCURACY OF PRESIDENTIAL PREFERENCE PRIMARY POLLSThere is widespread agreement that national opinion polls have done agood job of predicting presidential elections in the last two decades.There is much less confidence in the ability of state polls to predictthe outcomes of presidential preference primary elections. Indeed thenational polling organizations typically shun these state elections. Thestate polls are conducted either by local polling groups such as the FieldPoll in California or by pollsters hired by local or national media. Weexclude from this discussion polls commissioned by candidates, since thesepolls are usually released only as part of the campaign strategy of a can-didate and are often incomplete and distorted.An analysis of primary polls in the 1972 and 1968 elections reveals,however, that state polls have generally been reasonably accurate in pre-dicting primary results. Their accuracy depends mainly on the time spanbetween the poll and the primary election. Attitudes of voters in primaryelections, particularly presidential preference elections, are far morevolatile than in regular elections. Last-minute campaign activities, thevisit of the candidates and the impressions they make, and the results ofother primaries held a week or two earlier all affect the outcome. Thus,it is not surprising that there are major changes in poll results as thetime of the primary draws near. Polls completed in the week before theprimary are, in every case, better than earlier polls in predicting actualprimary results.-2-The results for selected primaries in 1972 and 1968 are given inTable 1. These are all the primaries for which poll results were reportedin The New York Times Index . While the list includes all the major primaryelections where polls were conducted, some other state polls may have beeninadvertently omitted.As may be seen, the average difference between the final poll andthe primary results was about four percentage points. Since most of thepolls reported here were based on sample sizes of about 400 persons likely.to vote in the primary, deviations of about five percentage points for theleading candidates and three percentage points for lesser candidates wouldlikely be due to sampling variability. While these sampling errors arelarger than for national elections, there do not appear to be major biases.The major differences between the polls and the primary results ob-served in Table 1 are in the 1963 New Hampshire and 1972 Indiana primariesand in the general underestimation of the vote received by George Wallacein the primaries. The gross underestimate of the McCarthy vote in NewHampshire in 1968 is almost certainly due to the polls being conducted beforethe serious door-to-door campaigning occurred. Particularly in the earlierprimaries, polls must be conducted until election eve if they are to beaccurate. The 1972 New Hampshire poll results were conducted into thefinal week and were much nearer to the election results.The Wallace vote in the primaries was underestimated 19 percentagepoints in Indiana, 8 in Florida, 7 in Wisconsin, and 5 in Massachusetts(but overestimated in California) in 1972. While some of the difference-3-in Indiana was due to the earliness of the poll there, one can only speculatethat Wallace voters generally find t*.e polls more threatening and are probablydisproportionately represented among undecided voters. (For the purposes ofthis analysis, undecided voters are excluded from the percentages, which hasthe same effect as allocating them proportionately as are decided voters.)Table 2 gives an index of dissimilarity between each state sample surveyand the actual primary results for that state. This was calculated by summingthe absolute values of all percentage differences and dividing by 2. An indexof 0% would indicate a perfect prediction, while any number larger than thatindicates what proportion of the respondents would have had to vote dif-ferently to reproduce the actual outcome. The indexes of dissimilarity rangefrom 4% to 57%, with a mean of 18% and a standard deviation of 13%. Thecorrelation between the number of days between the poll and the election tothe inaccuracy of the poll as measured by the index of dissimilarity is .75^indicating that 56% of the variance in the accuracy of polls is explained bythe number of days before the elections. It is clear that the accuracy ofpolls greatly increases as the election draws near. For instance, the fivepolls conducted one or two days before the primary election had indexes ofdissimilarity with the final election averaging 6%, even though several can-didates were running.The errors observed in primary polling indicate that the electorate isnot segmented into predictable blocs to the extent of the national electorate.However, as the election draws near, public opinion crystallizes to the extentthat an outcome is predictable with reasonable accuracy. Use of larger samples-4-would further increase predictive strength, though this is expensive whenprimary voters are a small proportion of the general population.In addition to predicting specific elections, the primary polls showthe trend of the relative strengths of candidates during the pre- conventioncampaigning. To illustrate this, we selected two major Democratic candidateswho entered most 1972 primaries* Edmund Muskie and George McGovern. The ratioof their strength was calculated fcr every primary poll and election. These17 measures were placed in chronological order and are given in Table 3.Muskie* s strength vis-a-vis McGovern declined steadily from a ratio of 4.6in a Florida poll of January 9, 1972, to a ratio of .04 in the Californiaprimary election. It appears that the actual elections and the sample surveysare both measuring the systematic and fairly orderly changes in candidate strength.Most of the state polls use telephone procedures. This has the majoradvantage of making it possible to complete the poll in a short period of timeand thus to measure trends over time. It is especially useful if a poll isconducted in the week before the primary. The results suggest that the minorityof households without phones are unlikely to vote in primary elections and thusno serious sample biases result. Although the phone procedures oversaraplewomen, the high correlation between the voting behavior of members of the samehousehold again prevents serious sample biases due to the underepresentationof men. Since time is the critical factor in primary election polls, it isclear that a timely phone poll will be more accurate and useful than a carefullyconducted face-to-face survey that is several weeks or a month old,for persons who wisii to predict primary election outcomes early, the simpleenumeration of a poll is of limited utility. Further analysis of the general-5-trends observed in earlier primaries will need to be carried out. Externalinformation about a candidate's organization and campaign tactics will needto be combined with survey data to improve the accuracy of predictions. Thelimitations of polls for predicting elections several weeks later are notattributable to technology or methodology but rather to an accurate readingof the situation, namely that positions can change rapidly in primary elections.-6*TABLE 1PRIMARY POLL PREDICTIONS AND ELECTION RESULTS 1972 AND 1968Primary Poll Predictions Election DifferenceA. New Hampshire (19!11) 2/18 2/25 3/5 3/7DemocraticMuskie 71% 54% 52% 48% 4%McGovern 23 34 33 35 2Yorty 4 6 5 7 2Other 2 6 10 8 2RepublicanNixon 80 78 71 6McClosky 14 16 19 3Ashbrook 6 6 10 4B. Florida (1972)DemocraticWallaceHumphreyMuskieJacksonMcGovernLindseyChisolmOthers1/9 3/2 3/1428% 34% 42% 8%24 18 1823 18 9 98 11 13 25 5 6 14 11 7 42 4 46 1 1C. Wisconsin (1972)DemocraticMcGovernWallaceHumphreyMuskieJacksonOthers3/23 3/30 4/423% 28% 30% 2.11 15 22 725 22 21 118 16 10 617 14 8 66 5 7 2D. Massachusetts (1972)DemocraticMcGovernMuskieWallaceHumphreyMillsOthers4/16 4/24 4/2646% 47% 48% 1%33 21 22 1{ 4 9 5\ll 15 874 4{ 9 9(Tal>le 1—continued)-7-TABLE I—ContinuedPrimaryE. Indiana (1972)DemocraticHumphreyMuskieWallacePoll Predictions Election Difference4/20 5/246% 47% 1%32 12 2022 41 19F. California (1972)Democratic 2/1 5/1 5/30 6/6McGovern 8% 35% 53% 45% 7%Humphrey 26 39 30 42 12Wallace 9 6 3Muskie 32 13 1 2 1Others 31 13 6 5 1G. New Hampshire (1968) 2/22 3/4 3/12DemocraticJohnson 86% 85% 50% 35%McCarthy 14 15 42 27Others 8 8RepublicanNixon 75 80 5Rockefeller "5 11 4Others 10 Q 1H. California (1968)Democratic 3/19 5/25 6/3 6/4Kennedy 46% 45% 46% 46%McCarthy 20 29 37 42Others (Johnson) 34 26 16 120%54I. Oregon (1968)Democratic 5/27Kennedy 38%McCarthy 36Humphrey 11Johnson 105/2837% 1%43 77 413 3-8-TABLE 2PRIMARY POLL ACCURACY RECORDYear State PartyNumber ofDays beforeElection1972 N.H. D 181972 N.H. D 111972 N.H. ' D 21972 N.H. R 111972 N.H. R 21972 Fla. D 651972 Fla. D 121972 Wise. D 121972 Wise, D 51972 Mass. D 21972 Ind. D 121972 Cal. D 1261972 Cal. D 361972 Cal. D 71968 N.H. D 191968 N.H. D 81968 N.H. R 81968 Cal. J 771968 Cal. D 101968 Cal. D 11968 Ore. D 1Mean 21Standard deviation 31Index ofDissimilarity22%559725122012720571912363552214471713-9-TABLE 3RATIO OF MUSKIE/MCGGV *N SUPPORT BY DATEDate1/9/722/12/182/253/23/53/73/143/233/304/44/164/244/265/15/306/6Polls4.64.03.11.63.61.5.78.57.72.45.37.03Primaries1.41.5.33.46.04UNivERsrrv of illinois-urbana30 12 060296750LnimHiHhHHH"HiBnisitlBlilIUHhHIHI 11HiJH fgtiBBttB098 HTBilll«HHW3«fiX**»2HimmmSSaAwSSneS

The accuracy of presidential preference primary polls / 196

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