Primary Mechanism of Candidate Engagement

In the context of United States elections, voters often choose candidates based on various factors including party affiliation, individual beliefs, and campaign strategies. One significant component during election campaigns is advertising, which aims to inform voters about the candidates' stances, achievements, and appeal. Understanding what contributes to a candidate's ability to gain support is vital for analyzing American political participation.

Which of the following is the primary mechanism by which candidates engage with potential voters during a campaign?