The South Carolina primary poll was based on 2,381 questionnaires completed by voters on Saturday evening as they left 35 voting places across the state. The poll was conducted by Edison Research of Somerville, N.J., for the National Election Pool, a consortium of ABC News, The Associated Press, CBS News, CNN, Fox News and NBC News.

The results are based on interviews with voters entering randomly selected precinct sites and are subject to a potential sampling error of plus or minus 3 percentage points. Results based on smaller subgroups have a larger potential sampling error. In addition to sampling error, the practical difficulties of conducting any survey of voter opinion on primary day, like the reluctance of some voters to take time to fill out the questionnaire, may introduce other sources of error into the poll.

Prof. Monika L. McDermott of Fordham University and Michael R. Kagay of Princeton, N.J. assisted The New York Times in its polling analysis.