Data from a series of surveys of voters in the Midwest, conducted during the 1976 presidential election campaign, were used to explore the effects of the campaign in relation to when people decided for whom to vote. A second purpose was to consider the adequacy of the traditional dichotomous model of voters: people who make up their minds early pay close attention to the media campaign, while people who make up their minds late pay little attention to the media campaign. The results indicated the following: exposure to the campaign is necessary for media effects; partisan precommitment is sufficient to prevent those effects; in the absence of precommitment, those exposed to the campaign will make their decisions on the basis of its content; and in the absence of precommitment, those who are not exposed to the campaign will vote on the basis of prior party identification. Finally, those who decided for whom to vote during the campaign made up 40% of the sample. (TJ)