Edmund Burke believed that after one was elected he must vote according to conscience, not the opinions of those who elected him and ofcourse, then be willing to lose his office in the next election.
The movie "1776" had some great lines. (A must see movie, IMHO)
[During the vote on independence]:
Dr. Lyman Hall: Mr. President, Georgia seems to be split right down the middle on this issue - the people are against it, and I'm for it.
[laughter]
Dr. Lyman Hall: However, I'm afraid I'm not quite certain whether representing the people means relying on their judgment or on my own. In all fairness, until I can figure that out, I'd better lean a little on their side. Georgia says nay.
Later in the film, he finds John Adams alone in Congress:
Dr. Lyman Hall: I'm sorry if I startled you. I couldn't sleep. In trying to resolve my dilemma I remembered something I'd once read, "that a representative owes the People not only his industry, but his judgment, and he betrays them if he sacrifices it to their opinion."
[He smiles] It was written by Edmund Burke, a member of the British Parliament.
[He walks to the tally board and changes his 'nay' vote to 'yea' on Independence]
There's plenty more HERE, including these gems, which always got a roar of approval from the audience:
John Adams: I have come to the conclusion that one useless man is called a disgrace; that two are called a law firm, and that three or more become a Congress! And by God, I have had this Congress!
John Adams (complaining to God): A second flood, a simple famine, plagues of locusts everywhere, or a cataclysmic earthquake, I'd accept with some despair. But no, You sent us Congress! Good God, Sir, was that fair?