Data collected as part of a larger survey that focused on the 1978 gubernatorial race in New York State were used in a study of political advertising and media credibility. Specifically, the study examined the factors that influence an individual's rating of the helpfulness of political advertising and related these factors to voting patterns. A telephone survey of 708 adults elicited information about their interest in the campaign, personal views on several political issues, media use, candidate preference, and political advertising, as well as demographic information. Among the findings were the following: people with less education tended to select television as the most credible medium; those who read newspapers regularly were slightly more likely to select newspapers as having the most credible political advertising; and more women than men found political advertising helpful. A positive relationship was found to exist between the medium selected as most credible and the types of reasons for selecting one's candidate: more people who selected newspapers as most credible for political advertising tended to cite issue-related reasons while those who selected television tended to give job-performance reasons. (Author/FL)