So-called "Super Delegates" were added to Democratic conventions long ago as part of the party organization leadership's backlash against reforms which followed the protests against the 1968 Chicago Democratic convention. The idea was to give the leaders and those whom the leaders would appoint a buffer against insurgent candidates supported by mass forces. What is happening today though is an example of how mass forces can change the balance of power, even against institutions and structures designed to stop them.
In Brooklyn, New York, a Congressman and Super Delegate supporting Hillary Clinton is the target of an extensive campaign by his constituents, who voted overwhelmingly in the Democratic primary for Obama. Although the Super Delegates can change whom they support (they are not pledged to anyone by the rules of the convention as are the regular delegate, and they can, if they wish, hypothetically vote for Clinton even if they say they are going to vote for Obama or simply not say whom they will vote for until the vote) the mass movement developing around the Obama campaign is beginning to put more and more pressure on these Delegates, making it difficult for them to vote for Clinton, especially if they are still elected officials and have pro Obama constituencies.
It is interesting that former Senator Fred Harris of Oklahoma, who ran on one of the most left oriented platforms in the 1976 Democratic primary contests (the press called him a "populist" and did what they could to ignore him) has endorsed Obama.
Actually, the most famous "uncommitted" Super Delegate is Al Gore. From my readings, he has no love of Bill Clinton. He also has developed enormously since 2000. Although this may very well be wishful thinking, his endorsement might really strengthen the mass movement and give Obama a momentum that would be unbeatable. As someone who went from the old politics of the Democratic Leadership Council and the Clinton administration to a "new politics" which has seen him become a global statesman of environmental movement, it would be fitting for him to help bring a new and necessary political period in U.S. history to fruition.