Final answer:
Congress plays a role in national discourse by setting the national agenda and influencing foreign policy. The media influences the public and policymakers, although its impact on Congress is often focused on local issues. Public opinion gives elected officials insight into the public's policy preferences.
Step-by-step explanation:
The role of Congress in national discourse primarily includes setting the national agenda, influencing foreign policy, and to a lesser extent shaping public opinion and regulating the media. Congress sets the national agenda by identifying problems needing government attention and proposing legislation to address those issues. The agenda-setting role of the media can influence both the public and policymakers, including the President and Congress, by deciding which issues deserve public attention. However, the media's influence on Congress is more limited compared to its influence on the Presidential agenda and tends to focus on local issues.
Public opinion is another critical component of national discourse as it enables elected officials to gauge the public's desires through clear signals about what policies should be prioritized. The media, as a socializing agent, helps in shaping public opinion by covering certain issues and thus has an impact on the agenda that Congress might set. Nevertheless, whether there is a true balance of power between the political arena, the public, and the media as gatekeeper is a complex question that may not have a straightforward answer.