I have two thoughts based on his speech and the reporting around him from last night:
1) Obama has obviously read that MBA classic, Leading Change by John Kotter. "Change agent"? Classic stuff; very useful.
2) Despite the incredulous wonder of the commentariat, it's not a miracle that Obama can win intra-Democratic contests and probably national elections in the 95 to 98% white Northern states. It's going to be a miracle if he can pull it off in more diverse places like South Carolina, where history and hate are more explicitly intertwined. They are going to Harold Ford him everywhere south of the Mason-Dixon.