It was meant to be a quick message on a reporter's voice mailbox. But the caller, a New York political power broker, apparently forgot to hang up the phone, inadvertently revealing his conversation last week with two associates that provided a rare glimpse into the otherwise tightly scripted world of mayoral politics. In the conversation, the three discuss a competitive Democratic primary as anything but that, treating it as a mere obstacle for the candidate, Fernando Ferrer, before he faces his big test: running in the general election against one of the richest men in America, Mayor Michael R. Bloomberg....