Fear that the Internet promotes harmful political rumoring is merited but not for reasons originally anticipated. Although the network accelerates and widens rumor circulation, on the whole, it does not increase recipient credulity. E-mail, however, which fosters informal political communication within existing social networks, poses a unique threat to factual political knowledge. A national telephone survey conducted immediately after the 2008 U.S. presidential election provides evidence that aggregate Internet use promotes exposure to both rumors and their rebuttals, but that the total effect on rumor beliefs is negligible. More troublingly, the data demonstrate that rumors e-mailed to friends/family are more likely to be believed and shared with others and that these patterns of circulation and belief exhibit strong political biases.