Final answer:
The Internet, including social media, is the most effective medium for reaching voters in the 18-to-30 age group due to its widespread use among this demographic and the cost-effectiveness of digital campaigning compared to traditional media like radio and print. So the correct answer is D.
Step-by-step explanation:
The most effective medium for reaching voters in the 18-to-30 age group would be the Internet. Given that younger people, particularly Millennials and members of Generation X, are more inclined to obtain news and information from digital sources, the Internet has proven to be a highly effective platform for engaging this demographic.
Radio and print media, such as newspapers and magazines, have seen a decline in effectiveness, particularly for political advertising, as they typically resonate more with an older audience. Furthermore, targeted messages through social media platforms like can be disseminated at a lower cost compared to traditional broadcast media.
Considering the widespread ownership of smartphones and tablets, coupled with the increased propensity of younger users to access news through these devices, an Internet-focused campaign strategy is optimal. This is supported by the data from the Pew Research Center for People and the Press, which indicates a significant increase in the consumption of news from digital sources among the U.S. population from 2004 to 2012.