A survey of the superdelegates by The New York Times that was completed a week ago found that 204 had decided to back Clinton, 99 backed Obama and the rest said they were undecided or did not respond. The survey came before the coast-to-coast contests on Tuesday, and the superdelegates can change their minds at any time.

The superdelegates include all Democratic governors and members of Congress, as well as officials and other prominent members of the party.

Obama, talking to reporters in Seattle on Friday, said he believed superdelegates should follow the will of the voters. "My strong belief is that if we end up with the most states and the most pledged delegates from the most voters in the country, that it would be problematic for the political insiders to overturn the judgment of the voters," Obama said. "I think it is also important for superdelegates to think about who will be in the strongest position to defeat McCain in November."

Clinton disputed Obama's interpretation. "If Senator Obama and his campaign continue to push this position, which is really contrary to what the definition of a superdelegate has historically been, I will look forward to receiving the support of Senator Kennedy and Senator Kerry."