Kathryn, from a purely pragmatic point of view, why would the Democratic super-delegates be swayed by the argument that they can expand their margins in a population that represents a small proportion of the national vote, and votes 90-percent Democratic anyway? The racially polarized results from Mississippi did not help the Obama campaign. Reinforcing that argument would not be persuasive in my opinion. I think Obama will have to show (and to an extent has shown) he can reach beyond that group to be viable.
Generally speaking the super-delegate vote is going to be retail not wholesale — i.e., it will come down to individual appeals, interests, promises, deals, and so forth, not large scale issues or intangibles like electability, whatever that is. And unlike other years, the membership roster of the DNC Convention Credentials Committee is going to be vitally important and is no doubt already being contended fiercely with the three co-chairs. Since that committee will decide who votes and who doesn’t, its composition will have a huge, perhaps decisive influence over who the nominee will be. Furthermore with a race this close it will go beyond the question of what to do about the Michigan and Florida delegations. In a situation in which every vote counts, expect to see a number of challenges designed to alter the pledged delegate count from other states using every reasonable and unreasonable argument you can imagine. I think Team Clinton will have the advantage here, both in terms of networks inside the party, and general ruthlessness.
So while all that is going on behind the scenes, publicly each side trudges along and hopes for the other side to make a mistake. With Obama having comparatively less national campaign experience, odds favor his team stumbling somehow. But of course had the highly experienced Clinton campaign not created its own train wreck, the candidate would not be where she is today.