WASHINGTON — F.D.R.'s secretary of the Navy, Claude Swanson, gave us this political adage: "When the water reaches the upper deck, follow the rats." This lugubrious saying is called to mind by the way the chairman of the Dean campaign stabbed his candidate in the back on the eve of his do-or-die Wisconsin primary. Steven Grossman, former chairman of the Democratic National Committee, knew that his last-minute defection would dominate the final-day news and crush Dean's hopes of a stronger-than-expected showing. What drives an old pro to such political disloyalty? Was Grossman trying to win his way back into John...