With Pennsylvania seemingly stuck solidly in Clinton's column (no real movement in the polls, but it's way too early to add it to her delegate total), the key states remaining in the Democratic primary process are Indiana, North Carolina, and Oregon.
I think Indiana is the most interesting case, and certainly the one "must win" Obama has left on his schedule. He's doing well in North Carolina and should win that with a small delegate plurality in the urban and university counties, with Clinton eating up large parts of the suburban and rural vote. Oregon could be a hotly contested state, as it's sandwiched between California (strongly Clinton, with some Obama strength up north) and Washington (one of the few states that Obama won clearly across the board), but it should ultimately fall to Obama.
I call Indiana a "must win" for Obama, because should he fail to win Indiana, he will have failed to win any Ohio valley state (Kentucky and West Virginia look to be strongly Clinton), and Clinton will have a delegate map that stretches in one continuous line across the heart of America, from sea to shining sea, which will be her motto heading into the superdelegate courtship.
Should Clinton win Indiana, she can make the case that Obama wins in states that aren't going to vote Democratic anyway (deep South and Plains states), while she captured states that are crucial to a Democratic win. You've heard her test this strategy after Ohio, and it's among her strongest cases for the nomination.
Much has been made regarding recent statements from superdelegates about respecting the "will of the people."
Two observations to made here: First, this is one of the clearest examples of what I like to call "Polispeak." You say one thing that can be understood in several ways, and you leave it to the recipient to hear what they want.
Charles Degaulle was a master of this. I suspect Obama might even be better at it, but since he's never had to put his money where his mouth is, we may never know.
The question hangs on the meaning of "the people". Do you count the popular vote? Well, yes, Obama should win, except his totals include large numbers of Republicans and Independents, as well as the lion's share of caucus votes, which are cast over a number of hours, hours that "the people" can't really spare from the business of paying the mortgage. Whittle it down to registered Democrats who voted in primaries...you know, the people who cast one vote each, the American way...and Clinton wins in a walk.
Delegates pledged? True, Obama has a lead here, but not enough to put him over the top. The people have spoken and neither Clinton nor Obama has won enough of their support to engage the nomination on the stump, meaning "the people" don't have a clear preference.
Second, superdelegates were put in place precisely to thwart the will of the people. The perverse logic that might drive many superdelegates (mostly elected Democratic officials) is that, since they represent their "people," as with legislating, they are chooising for the people.
My suspicion is superdelegates are leaning towards Clinton (they prefer insiders) but are looking for a compelling reason to vote for Obama. Indiana might give them that reason.