Ferraro, in a letter
to Clinton announcing her resignation from the campaign:
The Obama campaign is attacking me to hurt you.
Of (limited) interest: When Samantha Power left, her resignation statement
went out of the way to say something positive about Hillary Clinton:
“I made inexcusable remarks that are at marked variance from my oft-stated admiration for Senator Clinton and from the spirit, tenor, and purpose of the Obama campaign.”
Which makes it pretty clear that the Obama campaign has deliberately decided on a "classy" approach to these kind of incidents. It carries the risk, in the short term, of looking weak (i.e. not a "fighter"), but over time makes his campaign style very appealing.