The most effective response to how Kennedy's rhetorical question advances his appeal to voters is:
He wants his voters to think about how the United States should be broadcasting many more Spanish language programs in Latin America to promote democracy.
This response captures the essence of Kennedy's concern about the influence of Communist propaganda in Latin America and underscores his commitment to countering that influence through increased U.S. broadcasting efforts. By highlighting this issue, he positions himself as a proactive leader who values the importance of promoting democracy and engagement with Latin American countries. This appeal resonates with voters who are concerned about the spread of Communism and the United States' role in that region.