A related thread; see my post #19: On what basis should lawmakers make laws? - Great Debates - Straight Dope Message Board
I think Polycarp gave the best answer I’ve heard to that question. I seem to remember from my civics courses lo, these many years ago, that there’s a difference between Senators and Representatives here, however. I can’t seem to find it in the Constitution, so perhaps someone more informed than I can help me out here.
I remember learning that a member of the House was elected to represent his/her district, and the needs of the district were paramount in each Representative’s decisions. Members of the Senate, however, were supposed to put the welfare of their country ahead of the welfare of their individual districts. Is this right?
That’s been how things have worked out, kind of and sometimes, more or less, although it’s not specified in the Constitution that way. And of course, a senator’s “district” is his or her state. Senators have tended to take a more national outlook on issues than members of the House, but not always. Some political scientists think that the shift to direct popular election of senators (Amendment XVII, ratified in 1913) has made the Senate less committed to the national good - and more focused on “what appeals to the folks back home” - than it used to be. YMMV.