The results are based on interviews with 1,660 voters entering 40 randomly selected Democratic caucus sites. Samples are subject to a potential sampling error of plus or minus four percentage points. Results based on smaller subgroups, like supporters of a particular candidate, have a larger potential sampling error. In addition to sampling error, the practical difficulties of conducting any survey of voter opinion on caucus day, such as some voters changing their mind after they enter the caucus, may introduce other sources of error into the poll.

The Iowa caucus poll was based on questionnaires completed by voters on Monday evening as they entered party caucus sites throughout 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 Times was assisted in its polling analysis by Prof. David R. Jones of Baruch College in Manhattan and Michael R. Kagay of Princeton, N.J.