Question

in what way is social media primarily useful to campaigns?
citizens can vote via social media.
social media is convenient for polling.
campaigns can reach voters directly.

Explanation:

Social media's core value for campaigns lies in its ability to bypass traditional intermediaries and connect campaigns directly with large, targeted groups of voters. Voting via social media is not a standard or primary use, and while polling is a feature, direct voter reach is the most impactful and primary utility.

Answer:

Campaigns can reach voters directly.