Seeing a good possibility that the Democratic presidential nomination will not be settled in the primaries and caucuses, Senators Hillary Rodham Clinton and Barack Obama are lavishing attention on a group that might hold the balance of power: elected officials and party leaders who could decide the outcome at the convention in August.

There are 796 of them, and if neither Obama nor Clinton emerges from the primary season with the 2,025 delegates necessary to secure the nomination, they will in essence serve as tiebreakers. That is a result both sides see as increasingly likely.

Known as superdelegates because they are free to cast their votes at the convention as they see fit, they are the object of an intensifying and potentially high-stakes charm offensive by the candidates and their supporters. The Clinton campaign has established a system, overseen by one of the party's most seasoned behind-the-scenes operators, Harold Ickes, to have superdelegates contacted by carefully chosen friends and local supporters, as well as by big-name figures like Madeleine K. Albright, a former secretary of state. For particularly tough sells, the campaign has ex-President Bill Clinton or Chelsea Clinton make the call.

Obama has enlisted Tom Daschle, the popular former Senate majority leader, as well as Governor Janet Napolitano of Arizona and Senator John Kerry of Massachusetts, the party's 2004 presidential nominee. "You know there is something interesting going on when you pick up your cellphone and see all those out-of-state phone numbers," said Representative Gabrielle Giffords of Arizona, who reported getting calls from Napolitano and Daschle.

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