Elections are designed to hold officials accountable by providing voters with credible alternatives. In the U.S., a weak-party system means the decision to challenge an incumbent representative rests heavily on individual politicians' strategic calculations.

This study investigates how partisan media, specifically Fox News's haphazard expansion after its 1996 launch, influenced congressional elections during the 'Fox News Era.' We hypothesize that this media growth affected Republican potential candidates' perception of Democratic incumbents' vulnerability, thereby altering their entry patterns into electoral races.

Using district-level data on local Fox News availability, we find support for our hypothesis: Fox News significantly shifted Republican candidates' assessments of seat vulnerability, changing their decisions to enter congressional elections. This seemingly minor media expansion had a substantial impact on partisan competition and voter choice.