Incidental exposure to shared news on Facebook is a vital but understudied aspect of how citizens get involved with politics. This experiment investigates the influence of recommender characteristics (tie strength, political knowledge, political similarity) and different media sources (tabloids, legacy, and digital-born outlets) including multiple mediators(e.g., social pressure, outlet credibility) on incidental exposure to political news on Facebook. A 3 × 3 multi-stimulus, between-subject Experiment with two additional quasi-factors and 135 different stimuli was conducted using a representative sample (N = 507). Results showed that strong ties and recommenders with high knowledge increase news exposure, but the impact of knowledge is limited to recommenders with similar political opinions. Similar effects occur for different media types, which also have an independent impact on news exposure. Structural equation modeling reveals that media source effects are mediated through media perceptions, whereas recommender effects work via the desire for social monitoring and perceived issue importance.