Larry Bartels, a political scientist at Princeton University, has done some fascinating research on the responsiveness of U.S. Senators to the policy preferences of voters, broken down by income level. The above graph shows what happens when candidates have to spend so much of their time plying high-dollar donors for big checks to fund their increasingly expensive campaigns. As The New York Times noted today, Mitt Romney and President Obama have both held more fund-raisers than they have public events over the last seven days.
(via Princeton University)