The old Democratic heirarchy said goodbye to another of its fallen last night: former House majority whip and man-about-town John Brademas.

"Most political people, once they lose their jpower, lose their appeal," said party organizer Lee Kimche, "but not John. Of course, we're biased."

They were. But then, after 22 years and God knows how many markups, floor fights and Washington parties, Brademas has made a few friends. A good 400 turned up at a steamy Corcoran Gallery to eat, drink, sweat and listen to testimonial speeches chronicling Brademas from birth to the presidency of New York University -- his new job as of July 1. He lost his spot in Congress Nov. 4.

"Best election he ever lost," said Beatrice Brademas, his mother, who came to town for the party. "I was tickled pink because he was killing himself."

"My mother speaks," sighed Brademas.

The party cost $50 per person, which caused more than a few to figure it was a fund-raiser to pay off the $665,000 campaign debt. But no.

"We paid the bills," said Brademas.

So what the $50 actually paid for was dinner, drinks, hors d'oeuvres, the band and -- most remarkably -- the chance to see one of the biggest collections of merry-making Democrats since the Republicans moved in Jan. 20. There were people from academia, the arts and embassies as well, most notably Joseph Hirshhorn of the Hirshhorn Museum, British Ambassador Sir Nicholas Henderson and Daniel Boorstin, librarian of Congress.

But House Speaker Thomas P. (Tip) O'Neill (D-Mass.) was the attraction for the evening: He told a national television audience Sunday that he thinks the administration's tax-cut proposal is a "windfall for the rich."

"No compromise as far as I can see," O'Neill reiterated as he tromped up the steps of the Corcoran. "We're going to present a Democratic tax package."

The other attraction of the evening was Ephraim Evron, the Israeli ambassador, who found himself in a sticky diplomatic situation after his country bombed an Iraqi nuclear reacator over the weekend. Yesterday, the State Department condemned the action. "I hope that they would reconider," Evron said of the State Department. "This was an act of selfdefense. Absolutely."

"Hi, Mr. Ambassador," a passing guest called out. "Glad to see you with a smile on your face. Are you all right?"

"Is that the Israeli ambassaador?" another guest asked, utterly fascinated. "What's he saying about this morning?"

And so it went for Evron, presiding eye of the hurricane.

The party itself was more like a heat wave. In fact, it was. The Corcoran has raised only half of the $1.5 million it needs to install air-conditioning, so people perspired freely into expensive suits and silk dresses. But this being the nation's capital, hardly anybody removed his jacket. Finally, Sen. Paul Sarbanes (D-Md.) went to the microphone and said it was all right. Everyone obeyed.