John Sides finds some empirical support:
In Larry Bartels’ book Unequal Democracy, he finds that the voting behavior of senators is much more closely tied to the views of their upper-class constituents than the middle class or working class. One reason could be that upper-class people are more likely to vote, donate to politicians, and contact them to express opinions. But Mr. Bartels’s results persist even when controlling for the views of actual voters and those who have contacted their representatives. Mr. Carnes’s suggest another explanation: members of Congress vote as upper-class people would want them to because members of Congress tend to be upper class themselves.