The theory of representative government holds that lawmakers are the agents of the citizenry, who are deemed sovereign. Some members of Congress claim they will do what their voters want, but they usually evolve into thinking that they'll do what seems to be in their voters' best interests. They never forget that they can be held accountable, even for inconsequential but symbolic votes.
The Washington Post's Chris Cillizza has a valuable column with the numbers: only 15 Republican House members represent districts that voted for Obama in 2012; only one of the 14 GOP Senators up for election in 2014 comes from a state that voted for Obama. Thus, few Republicans have any political incentive to compromise with the President.
That kind of disparity is what the framers of the Constitution had in mind. That's why they gave the President, Senators, and Representatives terms of different lengths. I remember calculating similar figures when President Clinton was first elected: 98 Democrats were elected with more votes in their districts than Clinton. They had no incentive to follow his lead, and many didn't.
We onlookers who advocate civility and compromise and fiscal prudence are not asking lawmakers to commit political suicide. We are asking them to recognize that the national interest is at stake, and continuing prosperity. A good deal will have elements that each side wants, and smart voters can be persuaded of its value.