Howard Dean (DNC Chairman) understands it and so do Hillary and Obama.  Whoever loses this Democratic fight for the nomination has NO incentive to work for the victory of the Democratic Party in the fall.  Here's a list of the losing candidate in the last 7 presidential elections.
  Losing Presidential Candidate
    Year        Loser
    2004      John Kerry
    2000      Al Gore
    1996      Bob Dole
    1992      George HW Bush
    1988      Mike Dukakis
    1984      Walter Mondale
    1980      Jimmy Carter

    The losing candidate becomes a pariah in their party (for the most part).  The political insiders rarely give a loser a chance to run again as the head of the party.  (Adlai Stevenson 1956 being the exception).

    Hillary sees her current situation as win-win.  
    If she conitinues to fight for the nomination, she could ulimately win.
    However, even if she takes her fight all the way to the convention and comes up short, AND Obama loses in the fall.  She will be the lock-tight nominee for 2012.

    So the runner-up in the Democratic Nomination has NO incentive to work for the Democratic Candidate.  

    Howard Dean is the chief architect of this entire debacle.  I'm sure he's freshening up his resume as he'll likely get the pink slip before the new year.

    Finally, as an aside - look at the list above, one more time.  Each of the candidates on that list were leading in the Presidential polls in the summer before the election.  And each went on to lose.