This study investigated how people’s perceptions of the fakeness of Facebook posts and their intentions to take corrective actions are affected by the sources of those posts and their preferences for candidates in the context of the highly contested 2022 South Korean presidential election between Lee Jaemyung and Yoon Seokyeol. This study conducted an online experiment with a 2 (news source: in-group, out-group) × 2 (measured candidate preference: supporters of Lee, supporters of Yoon) between-subjects design (N = 537). The present study found that people’s perceived fakeness of an anti-Lee Facebook post differed depending on their candidate preference. The results also demonstrated that the source effect of the post on their perceived fakeness was moderated by their candidate preference. The differences in the perceived fakeness of the anti-Lee Facebook post between the out-group and in-group sources were significant only for those who support Lee. Finally, the current study tested a moderated mediation model and found that the source of the anti-Lee post influenced the intention to engage in corrective actions through perceived fakeness only for supporters of Lee. The implications of the findings were discussed.