Although Maxwell McCombs already had some interest in the field, he was exposed to Cohen's work while serving as a faculty member at UCLA, and it was Cohen's work that heavily influenced him, and later Donald Shaw. The concept of agenda setting was launched by McCombs and Shaw during the 1968 presidential election in Chapel Hill, North Carolina. They examined Lippmann's idea of construction of the pictures in our heads by comparing the issues on the media agenda with key issues on the undecided voters' agenda. They found evidence of agenda setting by identifying that salience of the news agenda is highly correlated to that of the voters' agenda. McCombs and Shaw were the first to provide the field of communication with empirical evidence that demonstrated the power of mass media and its influence on the public agenda. The empirical evidence also earned this theory its credibility amongst other social scientific theories.