IMO endorsements are over-rated and do not help a campaign much. Organization is what wins campaigns. Obama clearly has a good one and Hillary's has recently shown signs of cracking under the strain. But she is a seasoned, tough campaigner and her recent change in campaign managers could work to her benefit.
I don't see how she pulls it off - she'll need to get 56% of the vote in every single remaining election in order to go into the convention with more delegates. That is highly unlikely at this point - he's probably going to win Wisconsin and Hawaii easily (she isn't campaigning any more in Wisconsin, and he grew up in Hawaii). I think the vast majority of the super-delegates not yet committed will swing to Obama, and some of Hillary's committed delegates will change their minds (some already have).
I thought she was a good campaigner too, until this election. She had no "Plan B" if her "Plan A" failed. ("Plan A" was to be the inevitable choice, based on her name, money raised, her husband, etc.). She had to lend her campaign $5 million. Her campaign has made many poor choices, in other words.
Obama clearly has proven himself to be a smart and skilled campaigner, but don't count Hillary out yet. She is also very shrewed and her husband, if he can keep his mouth shut, is also a very skilled campaigner. I still would not count Hillary out. Obama is having a spurt right now, but he has not been in politics long and may not appreciate the need to manage a campaign to where he will peak in November instead of February or March. But I am a Republican and my be blinded by my desire to see Hillary running in the general election against McCain. Hillary will be easier to McCain to beat than Obama would be becuase of Obama's popularity among independents.
I think that Obama's lead is larger than it seems because there are many superdelegates out there who haven't chosen their candidate. Obama has won 8 straight states and as he keeps winning, those superdelegates will pledge their votes to Obama in order to avoid dragging the nomination into the Democratic Convention.
Obama is winning many smaller states. If he can't win at least one state out of Ohio, PA or Texas, it's all over for him. He is behind in all those states right now. A lot of small victories aren't nearly as good as a few big wins in this process. It is foolish to underestimate the Clintons.