A perspective from Vanderbilt University professor John Greer: When a candidate goes on the offensive to show the harm in an opponent's preferred policies or an inconsistency between an opponent's words and their actions, it helps set an important comparison point for voters.

When those attacks are false or play on the opponent's race, gender, ethnicity, or religion, it's under these conditions that attack politics harm democracy. Of course, it's important that attack politics, no matter how substantive, do not occur in a vacuum. The news media has to play an important role as "fact checker" and referee, something journalists failed to do in 2004 but have done a notable job so far in 2008, especially in the Obama v. Hillary race.