If a mark could be set at that level down to which the demotic politician is willing to stoop, it would most likely be set no higher than at that level up to which the majority of his constituents are willing to reach, so that there will be not too great a gap between them; and where there is a demand for a politician of a certain kind, we should not think that we will want for a supply, as Lord Salisbury wittily observed:
[I]f a Member of Parliament were obliged to dance upon his head for the amusement of his constituents, it is probable that men of fortune and independence would be found to do it, and to assure the spectators that the time devoted to the feat was the proudest moment of their lives. 
Some believe that such devotion is to be applauded as the surest sign that our politicians respond to the demands of their constituents. And so they do—as surely as a bladder responds to the demands of a bar-room binge.
 Robert Gascoyne-Cecil, 3rd Marquess of Salisbury, quoted by Andrew Roberts, Salisbury: Victorian Titan (London: Phoenix, 2000), p. 60.