Patterned after a 1976 study, a study examined voters' decision making during the 1980 campaign for the presidency of the United States. Data from a survey of 183 registered voters indicated that partisan voters were likely to be precommitted to a candidate choice and thus relatively immune to mass mediated campaign effects. However, those voters who made their voting decisions during the campaign varied in communication behaviors, candidate issue and image discrimination, and social structural variables. These voters were of three distinct types--campaign deciders, post-debate deciders (after the Carter/Reagan television debate), and last-minute deciders. Some of the differences across groups of voters, based on the time of their decisions, reflected similarities between this study and the 1976 study: ideological strength diminishes rapidly by time of decision; people with strong ideological stance, whether liberal or conservative, made up their minds early; and voters with below-average degree of ideological strength made up their minds just before election day. On the other hand, features of the campaign environment in 1980--most notably the candidacy of John Anderson and the timing and presence of a televised debate between the two major candidates--exerted substantial influence on the electorate, thereby distinguishing this study from the 1976 study. (RL)