The mayor of Philadelphia was sitting in the lobby of a downtown hotel yesterday morning, waiting for a panel discussion to begin, when he got a reminder of how different this Democratic convention has been for him from previous ones.

Michael Nutter received a call from a top aide to Hillary Rodham Clinton, asking if he would serve as master of ceremonies for a pre-roll-call reception of Clinton supporters from across the country. There, the New York senator would release her delegates and tell them she was voting for Barack Obama.

Nutter, an avid Clinton backer during the primaries, agreed to the request.

“It’s kind of like that old ad for Temple University,” he told a reporter after finishing the call. “She could have asked anybody, but she asked me.”