We identify a mechanism through which media concentration reduces political polarization and media competition (via specialization) increases polarization. This mechanism may help explain the patterns of US Congressional polarization. To avoid offending potential customers, a concentrated media seldom makes clear-cut endorsements and, as a result, provides little information. This leads to the convergence of party policy positions. Under competition, media companies specialize to a narrow ideological spectrum and, as a result, can offer strong endorsements without risk of offending customers. This leads to the divergence of party’s policy positions, that is, political polarization.