听力原文： The development of a mass culture dominated by the media has made major changes in the American political system, changes some observers feel threaten the very core of American democracy. In the 1940s the first studies were conducted to determine whether mass media was changing American voting patterns. The studies showed that opinion leaders, not the media, were directly affecting voter behavior, although the mass media played an indirect role by influencing the opinion leaders. This discovery led to the formulation of the two-step flow theory of political communication: the mass media influence opinion leaders, who in turn influence others. Follow-up studies in the 1960s and 1970s, however, indicated that the American political system was changing. The long-standing dominance of political parties was waning and political consultants were replacing party bosses. These consultants had advertising, public relations and opinion-polling backgrounds and had moved into the political arena to sell candidates directly to the American people through the mass media, much like others in their professions were selling soap and toothpaste. During the twentieth century, the mass media and political advertising began playing significant roles in selling political images. Television, which has become one of the most dominant forms of mass communication in our culture, has emerged as a powerful influence in determining the political destiny of this country. It helped create a winning image for little-known Senator John Kennedy, who narrowly defeated Vice-President Richard Nixon in the 1960 presidential election; led to a decline in popularity of Lyndon B. Johnson; allowed Nixon to win the presidency eight years later by building a more positive television image; and gave national exposure to a little-known peanut farmer and former Georgia governor, Jimmy Carter. By the 1980s the presidency had been turned over to Ronald Reagan, who had made his living communicating in front of the camera. Through his effective use of television, he was soon regarded as one of the most effective communicators ever to hold the office of president. American political candidates, managed by political consultants, are now using vote videos and direct mail as well as television advertising to get their messages across. Not everyone, however, gives TV so much credit for creating political images. Some studies have indicated that selective exposure, perception and retention play a bigger role in the election process. These studies contend, for example, that people project their own biases into television political commercials and see only what they want to see. News reporters have been criticized for running stories about candidates' personal lives, downplaying issues and focusing too much on who is winning. Television news has also been criticized for projecting winners on election night before the polls have closed in the west. This has kept many western voters away from the polls, critics contend. Not all campaign coverage by the media has been inadequate, however. Television has been instrumental in presenting presidential debates to the American public. Newspapers and some TV stations are now beginning to give better coverage of campaigns by analyzing political ads and reporting on their accuracy. It is hoped that such a trend will make advertisements more truthful and responsible. (56)