Last week, as one of the great rituals of democracy in America -- the filling of a Supreme Court vacancy -- was getting underway, democracy in Massachusetts was nearly getting mugged. Massachusetts is one of 24 states in which voters can approve or reject laws at the polls, a power they have had since the initiative and referendum were added to the state constitution in 1918. It is a power they have tended to exercise sparingly. From 1990 to 2004, for example, only 14 ballot initiatives became law -- an average of less than one a year. Why so few?...