Noam, asking "whether it's possible for the superdelegates to override the pledged delegates without provoking the kind of backlash that would doom Hillary" seems to me like asking whether magically transforming a duck into a cow would damage the resulting steak's flavor when tossed on the grill. Doesn't it jump the gun and too quickly assume the first proposition could actually happen -- that superdelegates might indeed want to select Hillary over Obama, so long as they didn't feel inhibited by fear of a black backlash? Because I just don't see, yet, any hard evidence of the first proposition, that superdelegates will want to override the pledged delegates come June. Yesterday Obama caught up with Hillary in Capitol Hill supers, snagging a particularly vulnerable and conservative Indiana Democrat, and Politico suggested the uncommitted ones privately favor Obama, too. The time for supers to sign on to Hillary out of fear Obama is unelectable is now, when they can point to the day's crummy headlines to back up their fears, not later -- and yet we haven't seen any surge for her; just the opposite. All the hypotheticals in the world about how the supers could overturn the pledged count without pissing voters off are a little bit moot, absent evidence there might be a movement to do so.
To some degree, I think this stage of the primary just isn't registering in people's minds as a zero-sum game. The Wrightmare has diminished faith in Obama, but it hasn't given anybody any new love or respect for Hillary.