"If the votes of the superdelegates overturn what happened in the elections, it would be harmful to the Democratic Party...The way the system works is that the [pledged] delegates choose the nominee."
So Maria Cantwell, the Junior Senator from the state of Washington, is in a club by herself. She is the only superdelegate who endorses Clinton, but will vote for Obama (absent a total collapse of the Obama campaign). She has not renounced her endorsement of Senator Clinton, she has simply said that the will of the people is more important than her opinion:
"If we have a candidate who has the most delegates and the most states,” the Democratic party should come together around that candidate, Cantwell said. The pledged delegate count will be the most important factor, she said, because that is the basis of the nominating process.