One thing that attracted me to Obama is his unwillingness to attack, he'll make contrasts with his opponents but he won't accuse them of eating little babies. This made sense to me, if you just discuss differences in positions, then your opponent looks bad when they start the attack ads. However
this article suggests that said strategy might not work. The article was originally under the header "Could Clinton-Obama fight hurt Dems?", notice the word "fight" and how it suggests that both are attacking each other. Yet the article doesn't list one instance of Obama attacking Clinton because there have been none, for example Obama's campaign never said anything about Clintons' MLK-LBJ comment.
I think ultimately this primary will tell us if this type of no attacks candidacy can work or if they don't. These types of primary stories don't make me optimistic but maybe voters will see through it.