Democrats filling the hotels, sidewalks, cafes, bars and restaurants of Boston and swarming through the FleetCenter this week have a message they desperately want the rest of America to hear. We are not liberal. These politicos will spend the bulk of this week insisting that the Democratic Party is the one that represents the values and ideals of Middle America. The Republicans, they will say, are the ones whose beliefs are so far beyond the norm that they simply cannot be trusted. Even the City of Boston is in on the act. The city, its boosters and local journalists are...