THE share of Americans who believe that news organizations are "politically biased in their reporting" increased to 60 percent in 2005, up from 45 percent in 1985, according to polls by the Pew Research Center. Many people also believe that biased reporting influences who wins or loses elections. A new study by Stefano DellaVigna of the University of California, Berkeley, and Ethan Kaplan of the Institute for International Economic Studies at Stockholm University, however, casts doubt on this view. Specifically, the economists ask whether the advent of the Fox News Channel, Rupert Murdoch's cable television network, affected voter behavior. They...