An evening of apparent contradiction was mellowed with white wine and cheese and the ballads of singer Harry Chapin last night as supporters of Mark Green, former director of Ralph Nader's Congress Watch project, gathered at a fund-raiser for Green's upcoming congressional campaign.

Long critical of Congress in his articles and books such as "Who Runs Congress," Green is running in New York City's 18th, or Silk Stocking, district. The seat was formerly held by John Lindsay and Edward Koch and currently belongs to Republican William Green (no relation). "Someone in my office answered 'Bill Green for Congress,'" said Mark Green, with a slight laugh.

Upon arriving at the Capital Yacht Club party, Nader said he had noticed Green's ties were becoming narrower and more often red, white and blue in color.

"The question is how is he going to behave when he gets to the House of Representatives. We're going to be looking very carefully at how he votes up there," warned Nader.

Green, however, seemed at ease with his defection from the watchdog role. "For all my criticism of Congress as often paralyzed, if not corrupt, I have a schoolboy-like reverence for the legacy and the potential of the institution," said the candidate.

The band played the "I Love New York" theme song as the 300 Washingtonians, many veterans or current members of Nader's Public Citizen organizations, munched soft pretzels smothered in mustard and hot dogs from a street vendor stationed on a deck overlooking the Potomac.

"Back in '68" and "Back in '62" began conversations in the crowd of three-piece suits and closely cropped beards, as the subjects of litigation and lobbying surfaced again and again. And clusters of summer interns gathered around their mentor, Nader. "I've admired you all my life," gushed one young woman.

Harvard economist John Kenneth Galbraith, a longtime friend of Nader and Green remarked, "When you look around this room you see people celebrating a new revival of liberalism. The test of liberalism in this country is the ability to withstand the perception of a great movement to the right."

Green said that he has been advised that, for a man with his liberal background, this might not be the best year to run. But he added, "It's never a good year if you want to change things and rock the boat." Later, he observed that in the 18th district he would represent large Hispanic neighborhoods, "the run in the silk stocking," as well as neighborhoods housing ice-cream boutiques.

"Next thing you know," he said, "they'll have designer pizza."