Final answer:
The cost of public relations has been lowered and it has become easier for interest groups to get their message to the American public primarily because of advancements in technology, particularly the Internet and social media.
Step-by-step explanation:
The cost of public relations has reduced with the rise of the Internet and social media, enabling interest groups to directly reach the public at a lower cost and bypass traditional media gatekeepers.
The advent of cable TV in the 1980s and the exponential growth of the Internet since the 2000s have facilitated a media environment where traditional gatekeepers of information are bypassed. Politicians, political parties, and interest groups can now directly reach an audience through social media platforms, use less expensive online advertising strategies, and engage in targeted messaging.
The concept of 'Astroturfing' reflects how interest groups can create artificial grassroots movements to influence public opinion. These strategies, along with tactics like email campaigns and interactive blogs, have allowed interest groups to disseminate their messages more effectively and at a reduced cost compared to traditional media outlets.