Final answer:
Direct mail advertising involves sending promotional materials such as postcards or flyers to potential customers. This method, while traditional, is distinct from television, radio, and online advertising.
Step-by-step explanation:
The form of advertising that involves sending postcards or flyers to potential customers is direct mail advertising. This method targets individuals using demographic data to send promotional materials directly to their mailboxes. With the emergence of new technologies, traditional forms of advertising, like television advertising and print media, have seen a decline in effectiveness as online advertising and social media platforms offer more targeted and immediate ways to reach potential consumers. In the context of political campaigns, while television advertisements provide widescale reach, especially among older voters, the increasing trend is towards more personalized and cost-effective online campaigns tailored to specific demographics.