Hanky Panky on the Potomac : HAPPY ENDINGS, <i> By Sally Quinn (Simon & Schuster: $22; 566 pp.)</i>

This year brought us the Clarence Thomas hearings, where upstanding Washington public figures appeared to be deeply shocked at hearing the word “penis” uttered in so august a place as the United State Senate.

And now comes Sally Quinn, former scorched-earth profile writer for the Washington Post and wife of the Post’s former editor, a Beltway insider if ever there was one, with her second novel. “Happy Endings” confides that Washington’s upstanding elite in fact throbs and burns behind its Windsor knots and pearls, and spends a great deal of time either in the sack or anticipating the sack, sometimes in the pursuit of true love.

Accurate, without a doubt, but rather behind the curve. Washington of late has been performing with a hypocrisy and hilarity that no fiction could match. It would take a Jane Austen to invent a character like John Doggett, and Sally Quinn is no Jane Austen.

On the other hand, many people may relish a book that confirms their most dismal suspicions that the body politic operates well only when it is prone.

Here is where “Happy Endings” (which shares characters with Quinn’s best-selling first novel, “Regrets Only”) takes us, en route to its double-hat-trick finish in Prague: The President is assassinated. His widow, Sadie, turns to her former lover, dashing Des Shaw (does he pronounce it Dez or Dess? We never find out), hotshot Washington journalist and the father of Sadie’s child. But Dez/Dess is rekindling an old flame with Allison Sterling, goddaughter of a former President, blond newspaperwoman, la belle dame sans merci , with whom Dez/Dess broke up once before because she beat him on a story.

Allison becomes the first woman national editor at her paper, and she and Dez/Dess try to make It work this time. Sadie-Sadie, ex-First Lady, falls for a married doctor over at the NIH, and to get her mind off this hopeless amour, tries to help the new First Lady, an uprooted country-western singer, find a Cause, not to mention a wardrobe purged of push-up bras and fringe.

The cause she finds is AIDS--a funny thing, because it turns out the President has AIDS and the doctor Sadie lusts after is treating him. He keeps Sadie at arm’s length, not because of AIDS worries but because he is Jewish and she is not.

Anyway, Dez/Dess and Allison marry and have a child who dies tragically shortly after birth. She drinks, he drifts. Dez/Dess thinks of joining Sadie and his son; Sadie thinks the same. Alas, they never think it at the same time. Indeed, much of the plot revolves around bad timing.

You’d almost take this for an Oprah transcript, except that somewhere in here is a presidential election and a drug scandal that brings down the attorney general. The plot comes up empty on civic passions, in itself a critique of a fatigued process and a capital city that jockeys for rank and notice like lickspittles at the French king’s levee, while outside, the sans culottes sharpen their pikes.

From her Post years, Quinn can supply vivid settings: the White House; the Pulitzer Prizes, where anxious editors pop in and out of the judges’ room like Feydeau characters; cozy Eastern Seaboard hideaways and 10 (I counted) Washington restaurants. More happens here over dinner plates than over desks, and finally we find out just how many Secret Service agents it takes to escort the President out to a meal.

By reputation, Quinn is flippancy incarnate. On paper, such repartee can look arch and contrived; with wit, as with charm, you usually had to be there. The same goes for sex: Her couplings come over as more ludicrous than lubricious--this from someone who once answered the hand-wringing of other women journalists with “Being blonde doesn’t hurt.”

“Happy Endings” is at its most feeling when it touches on what matters to Quinn now, her own mined truths of marriage and motherhood: a son with terrifying seizures like her own son’s, Superwoman conflicts of career and home.

The book rounds the bases on sexual harassment and women-as-tokens, on the navigational delicacies facing women bosses. There is an amusing who-gets-the-coffee schtick. Yet Quinn blows off editor Allison’s conflicts with an intractable reporter by a roll in the hay--not exactly management-handbook material.

Quinn, who wrote passionately against mothers serving in the Persian Gulf war, sounds more than just ambivalent about combining career and motherhood; she shuttles between angry and mawkish. Editor Allison is embarrassed at a reporter’s pregnancy, considering it “an affliction of some kind.” Then, 150 pages later, pregnant Allison “really didn’t want to be at work anymore. She wanted to be home knitting booties.”

Quinn’s post-Post life has taken her off the merry-go-round, and as she watches it go around without her, the question evidently occurs to her, as it has to others who have chosen to let go of the brass ring:

“They were all at the pinnacle of power . . . look at who they were . . . the President and First Lady, the former First Lady . . . a nationally famous television anchor . . . the most powerful woman in journalism, and one of the most distinguished scientists in America. All this success and power and money and fame. For what?”

Good question. If the best of Washington is a self-absorbed, inbred life among the political Jukes and Kallikaks, it’s enough to persuade you that legislative term-limits are nature’s way of renewing the gene pool of the governing class.

The most winning character here is the bewildered, in-over-her-head First Lady who wouldn’t know arugula from collard greens and longs only for country roads to take her home. If this book is the real Washington, I know how she feels.