An interesting article by Roger Kimball picked up via Instapundit. Here is the money quote:
Why do they tend to be dour people with no laughter in their hearts? Because they regard life as a zero-sum game. . . . Leftists are supposed to be the caring, sharing part of the political fraternity. In point of historical fact, it is an easy thing to demonstrate that their caring has always been more a rhetorical than an actual strategy and that their sharing has been accomplished overwhelmingly with other people’s goods. That said, however, there is still the fact that Leftists are hailed by their enablers as the non-crabby politicians, the people who come into office promising two things: More and Free.