That's the opposite of my point. If the Dems need a stepping stone between character assasinations and running a purely positive campaign, they could do like the GOP does: manufacture issues which look positive but are actually attacks. Flag burning being one perfect example of a purely manufactured passive aggressive attack campaign issue.
I'm saying if they really must go negative, let them do it by finding their own divisive gimmie fake issue versions of gay marriage and flag burning to energize their base.