HER CAPACITY to surprise Washington was evident even before the Congress to which she had been elected in the fall of 1974 got going. The Press Club of Washington had its annual congressional dinner, a kind of audition where newly elected, not-yet-installed members of the House and Senate are invited to give brief speeches -- and where the assembled incumbent establishment of Washington, in its inimitable and unendearing way, gives a thumbs-up or thumbs-down sign to the newcomers. Mrs. Fenwick, billed as a wealthy, aging, conservative Republican female from New Jersey who had blown away some liberal Democrat, was not exactly looked forward to with excitement. She was in fact penciled in by many to be the bore of the evening.

And then there she was. She was funny. She was sharp. She was graceful. She was wise. That is, she was Millicent Fenwick. The representative from Bernardsville, New Jersey, stole the show that night -- and it was pretty much like that where Millicent Fenwick was concerned for the next eight years.

Surely the element of surprise was key. It proceeded from the fact that Mrs. Fenwick is no doctrinaire, party-lining anything. She is independent, open-minded, accessible to argument but immovable on certain fundamental values she holds dear. The conservative Republican female from the wealthier reaches of New Jersey turned out to be a champion of women's rights, a social liberal and egalitarian on many issues, and a one-women conscience of American politics where the seduction of PAC-provided campaign contributions was concerned. She announced of such contributions that she would neither seek nor accept any in her Senate race. It is her belief that these are merely a dressed- up way of buying and selling votes.

Rep. Fenwick stayed faithful to this position, and her fidelity to it surely helped bring about her defeat. This town will miss her. It will also, despite its great capacity to avoid thinking about awkward, embarrassing things, take note of Mrs. Fenwick's particular protest against the way we have come to finance our increasingly costly campaigns. She fought the good fight, and she went out the same way she came in: with class.