Political polarization and the electoral effects of media bias

We develop a model in which profits of media firms depend on their audience ratings, and maximizing profits may involve catering to a partisan audience by suppressing information that the partisan audience does not like bearing. While voters are rational, understand the nature of the news suppression bias and update appropriately, important information is lost through bias and can lead to electoral mistakes. We characterize those conditions that give rise to electoral mistakes, showing that heightened political polarization and asymmetric distributions of voter ideologies make electoral mistakes more likely. Even if the median ideology is a centrist and centrist voters gain access to unbiased news, media bias can generate excessive "cross-over" voting, which, in turn, can lead to the election of the wrong candidate. (C) 2008 Elsevier B.V. All rights reserved.