Rep. Richardson Preyer (D.N.C.) was incorrectly identified in yesterday's Style section as a Republican. CAPTION: (NEW-LINE)Picture 1, Wiley Branton, Jack Greenberg and Vi Curtis Hinton at party commemorating Brown decision, by Margaret Thomas-The Washington Post.; Picture 2, Rep. Augusstus Hawkins, Coretta Scott King; by Joe Heiberger-The Washington Ppost; Picture 3, Edward Kennedy and Mrs. Peter Jay with Elizabeth Drew; by Harry Naltchayan; Picture 4, From left, Patricia Harris, Elizabeth Holtzman, Michael Blumenthal and Margaret Heckler; by Fred Sweets-The Washington Post.

"How can you tell the senators?" asked a woman as she surveyed the suits and ties at the Folger last night.

"Look." an experienced White House staffer told her, "they're the ones with the smoothest shaves and the perfectly clean shirts."

They were easy to spot, since senators made up the largest single group among the guests at a reception last night for The New Yorker's Washington correspondent, Elizabeth Drew, upon the publication of her new book. The senators were appropriately obvious, since Drew's book, a study of Iowa Sen. John Culver, is entitled simply. "Senator."

"Why didn't you bring the whole Senate with you?" Drew asked Vice President Walter Mondale. "You're in charge here."

Mondale apologized, saying the upper chamber was still debating foreign aid issues. He himself, called back to duty after pocketing a note from former Sen. William Hathaway, nearly decimated the reception in its early stages by withdrawing with a dozen Secret Service operatives.

But come the senators eventually did-"almost a quorum," a Simon & Schuster aide commented.

The Democrats held a clear majority: Senators Kennedy of Massachusetts, DeConcini of Arizona, Cranston of California, Hart of Colorado, Inouye of Hawaii, Muskie of Maine, Glenn of Ohio, Hollings of South Carolina, Jackson and Magnuson of Washington and even Majority Leader Robert C. Byrd of West Virginia.

A few Republicans, including Rep. Richardson Preyer of North Carolina and Sen. William S. Cohen of Maine, also attended.

There was a handful of White House faces (congressional liaison Frank Moore, Deputy Assistant for Communications Greg Schneiders, speechwriter Rick Hertzberg) and a smattering of ambassadors (Peter Jay of Great Britain, Count Wilhelm Wachtmeisterof Sweden, Robert Strauss of trade negotiations and Dick Clark of refugee affairs).

"Isn't this appropriate," said Deputy Assistant Secretaary of State Robert Hormats, gazing at the Tudor-era banners hanging overhead. He looked down at Drew and grinned, "This is, after all, an Elizabethan occasion."

Despite Drew's reputation for remembering a telling anecdote, her guests relaxed more and more as the evening progressed. Jackson grabbed a camera to catch Kennedyhs arrival; Strauss, over in one corner, took bets and gave odds on the Republican presidential nomination. Culver himself slipped out, at one point, for a final vote, then unobtrusively returned.

In between praising the book, Kennedy slipped into corners to press his case for national health insurance. "Medicaid. Medicaid. Medicaid. . ."

"Tell me," asked a rueful publishing representative. "Are all Washington parties like this?"

No, was the answer: some are more political.