AWARD-WINNING Washington architect Hugh Newell Jacobsen has designed a spectacular contemporary house for that million, ocean-front acreage Jacqueline Kennedy Onassis bought on Martha's Vineyard last year.

The fact of his having been chosen has been kept almost as secret as the Manhatten Project.

Onassis had conducted a wide-ranging talent search, picking the brains of her most artistic and creative friends, before she selected Jacobsen.

She had appraoched I. M. Pei, who designed the John F. Kennedy Memorial Library in Boston and the new National Gallery wing here. But Pei doesn't do houses.

Actually, Pei once sketched a house on the back of an envelope for Washington's Bill Slayton, former head of the AIA who is now in charge of the State Department's foreign housing.

Pei was persuaded into going up to the Vineyard and walking over Onassis' 356 upspoiled, wetland acres. He gave her his thoughts and guidance on what kind of a structure should go on that site.

Mrs. Paul (Bunny) Mellon, a perfectionist who knows more about the interiors and exteriors of houses than most of the professionals she pays to advise her on her own, has been working closely with Onassis on ideas for the house.

Jacobsen has done a lot of work for the Mellons, although he is almost as secretive about it as they are.

This will be the first contemporary home for Onassis.

Her lawyers have already filed for special permits to begin construction. Hearings are scheduled in Gay Head, Mass., on Dec. 28.

Nobody was happier to see that recent $1,000-per-person Carter fundraiser here sell out than the reelection commitee's former landlord at 816 connecticut Avenue.

The Carter-Mondale campaign headquarters moved out to larger offices, leaving the rent unpaid for at least two months. Dunning threats were to no avail, says one source who knows. For awhile, no one would even return phone calls. Then, someone did, to say that they were temporarily short of funds.

That wasn't an Iranian with whom former CIA director Richard Helms was lunching at the Sans Souci last week.

The gentleman was from Oman, Helms said, and has "something" to do with the Army.

The third person at the table was Jim Critchfield, an oil expert from Tetratec International and an "old friend" of Helms.

When hairdressers Charles I and Roi II wen their separate ways, Roi got custody of their famous swimming pool, with its mosaic mural of Marilyn Monroe in her nude calender pose.

He also got the half-million dollar house on Colorado Avenue, where he and Evelyn Sandground will give a Christmas party Dec. 22.

The invitations are probably the only honest ones ever printed for a Washington party. They announce "You are invited because . . ." and 23 reasons (with blanks for check marks) for which most people get invited to most Washington parties, if the truth were told.

They include:

"You are running for president.

"You are an elected official who has yet to be indicted.

"You're a journalist, so bring a pad and pencil.

"We'd like to get invited to one of YOUR parties.

"You have a Rolls Royce.

We never know when you might get to the top."

By mistake the post office dumped 100 copies of the new issue of The National Enquirer on a reporter last week.

A spokesman for the tabloid at first declined to do anything about reclaiming their misplaced property. "Give them away as Christmas persents," he said.

Then someone apparently discovered that particular bundle included a bunch of the free papers that are mailed each week to the household of every member of Congress.

A mailman was dispatched to fetch the complimentary copies and forward them on their appointed rounds.