The combined effect of advertising and news coverage in the Mexican presidential campaign of 2000

In July 2000, the PRI (Institutional Revolutionary Party) lost the presidency of Mexico after 71 years of continuous rule. Research based on individual data obtained with surveys shows that important media effects occurred. Using aggregate data, in this article the author explores the effects of political advertising and media coverage on preferences during the Mexican presidential campaign. Data on voter preferences are taken from results of a trial ballot question in public opinion polls. Data on advertising are measured in gross rating points. Data on media coverage are taken from the monitoring of newscasts on the two major networks. OLS regression models are developed, with preferences as the dependent variable and campaigning differentials as the independent variables. Based on aggregate data, this research shows that in Mexico's 2000 presidential campaign, exposure to political communication led to persuasion, and news appears to have been more important than ads. Political communication was a unified process where ads and news presence acted together in a very interesting fashion, "bounding" each other in periods of major changes in preferences but with news effects prevailing over ads. Qualified news differentials accounted for 20% of the variance in preferences, and ad differentials accounted for 8%. This media effect occurred through a cumulative process where ads and news coverage acted together.