I'll take a break from the Coronation Cup having just satisfied myself of the 1-2, in order to go over my thinking on this.
Not unlike the UK, with it's North/ South divide, there is no definitive official boundaries that demarcates the various sub-regions of the United States, but they exist in perceptions and have altered in line with demographic shifts and the various historical and cultural influences that have been brought to bear on the states in question. 'The South' still broadly conforms with the confederate states but as population has shifted from the industrial north to the post industrial south (especially retirees in Florida and economic migrants to Texas) subtle changes have occured.
Most definitions you'll find about the areas include the 'Deep South' and the 'Upper South'. The deep South remains pretty well stereotyped Republican country and includes Alabama, Georgia, Louisiana, Mississippi and the Carolina's (although North Carolina is often bracketed as the upper south). In any event, Clinton couldn't win one of these states amongst Democrat voters. Once Republicans are thrown into the mix, she'd have no chance of bringing anything to the party.
Texas and Florida are geographically of the same region, although culturally they tend to be seen as appendages given that they are essentially less (how can we put this?) perhaps I'll try for 'more open to outside influences and less traditional'. She did of course win Texas, but neither Democrat would reasonably expect to come November. Florida as ever, will remain the key state amongst the swing states, given it's contribution to the college. It's difficult to know if Hilary would have won there? The consensus is that she would, and she's counting their votes in her claim to have won the popular vote, but Obama never campaigned there, and it was a marked feature of all the caucauses and primaries that Obama was frequently chasing down, and over-taking Clinton leads, once he got going.
The states she won in the South were largely in the 'upper south' Arkansas for historical reasons and personal affiliations and Tennessee. You might add Oklahomo to the list as its sometimes considered an upper south state but tends to owe the assignation to an historical quirk that banded the land that is now known as Oklahoma into a kind of 'bad land' area that was loosely allied to the confederacy, by the same token, even Maryland is sometimes considered a southern state (which strikes me as being bizarre).
The Democrats will need to gain some of the southern states, and might face a slightly different dynamic this time round, given that McCain is a northern candidate who might yet represent the acceptable face of Republicanism. To some extent Hilary is regarded as a northern establishment figure, and not really an Arkansas person. She's essentially a Washington figure with a New York senate seat. Obama can obviously trade off his Illinois background, but it was notable that she tended to beat him in the traditional 'blue collar' vote in the nortern states. To some extent, he's going to need someone who can seal this gap for him, and there wouldn't be many obvious candidates.
He might risk taking the blue collar vote for granted? (would they vote for McCain?) or he might need someone who can reach out to the traditional democrat core vote, as well as being acceptable to the South? For his part Obama will bring the under 35's to the party, and the black vote. You might argue that Hilary would appeal to the female vote? but given the choice between Obama and McCain, I'd suspect that he's no less likely to be able to deliver this block too. His glaring weakness is in the South, and there's little if any evidence that Clinton can bring much to the party, although it wouldn't require much on the round of results, and somewhere like Arkansas might be enough yet. She was notably stronger in other battleground states though like Pensylvania and Ohio and this suggests that she still carries the blue collar traditional democrat voter, and that he hasn't quite taken this territory from her. I have little doubt that she could deliver this vote, but she's not the only Democrat who could either.
You might of course argue that neither candidate would win the deep south, and that Obama's lead over Clinton there is tantamount to inconsequential? (she does) and in fairness I wouldn't really disagree. Following that line therefore, he needs someone who can win the upper south, or at least achieve a degree of parity, whilst still doing enough to shore up the core vote.
For practical purposes I really don't see how he could have her as a VP, and I think there'd be a very real prospect of having two administrations emerging norty . We've seen splits in UK parties before, but I can't think of a case where an American VP has sort to puruse their own programme. This could easily happen on this ticket. My God, she was bad enough when she became first lady, heaven knows what she'd think she had a mandate to do if she was an official number 2 norty
) that prefer the discredited and futile isolationist route.
) but one of the reasons hes unequivocally supported by many on the left is simply because of his colour