A study of the agenda-setting influence of the mass media on adult viewers explored (in a series of five experiments) how political knowledge stored in long term memory can be activated by the media, leading to decisions about issue salience. Spreading activation theory formed the basis for the study, and priming--the concept that the activation of one thought causes activation of associated thoughts--was the method used to study the structure of memory. One hundred seventy-six participants (all from Travis County, Texas) were asked to view news stories and advertisements about 1988 presidential candidates George Bush and Michael Dukakis and about the issues of leadership and the economy. Findings included: (1) when the message content was held constant, the form of the message made no difference in either salience or knowledge scores; and (2) activation of memory favored pathways between knowledge nodes rather than between salience nodes. (An appendix listing the indexes used in the study, 39 references, three tables of data, and 12 figures are attached.) (MHC)