Shankar Vedantam has written for the Washington Post about psychological research on the effects of misinformation and how it applies to politics. Media Matters has a nice summary of some of the implications:
If Candidate A lies about Candidate B, for example, the fact that Candidate A is lying should be the lede – otherwise the news report just drills the false claim into readers’ and viewers’ minds, allowing the misinformation to take hold before it is corrected. As I wrote in my column on Friday, the news media too often privileges lies rather than punishing them.
Lies need to be debunked in the right way, or there can end up being a boomerang effect.