Ellen Marcus, Democratic Lady Tried, True and Blue will be in yet another wave of Americans going to China, when the board of the National Trust for Historic Preservation leaves next Friday. She is flying to the coast a little early to visit family in San Francisco, and then with the Trustees on the usual China route . . . Hawaii, Hong Kong, Canton, Peking, Souchou, Shanghai.

Living out of a flight bag has been Ellen's story this year. She's been to Ireland, Alaska by ship with old Stanford classmates, and now off to the inest place there is. Coming back stateward, Ellen will visit the Charles Blacks in Hawaii, will dawdle in Tokyo and end up in San Francisco again, this time for the National Trust annual meeting.

Demo fund raisers and planning sessions are sterile things, indeed, if Ellen isn't in on them, so it makes sense that she was included in the Friends for Kennedy gathering last week at the Maison Blanche . . . the eatery, not the W.H.

That New Hampshire political lady with the great name, Dudley Dudley, whom Ellem describes as "the Ann Harding type . . . a total 'personage' . . . the N.H. equivalent of their lieutenant governor . . . descended from Daniel Webster and everybody else good and aristocratic in New England you can think of," was making stirring remarks to a restaurant full of old Jack and Bobby K. workers as well as Johnson, McGovern, and McCarthy campaigning vets.

With "low-voiced directness and her face shining with skin like marble without a pore to her name" (another Ellen quote), Dudley Dudley has gone past Draft Kennedy rumors, she is working diligently on the reality of same, exhorting party regulars to join up early, asking them to come on up and help in the N.H.February primary, an event, which legend says proves which one is going to be president.

Washington's Horsey People will have a party with hardly an excuse, so they got together last week at True Davis' stone mansion on the ravine side of Woodland Drive to plot the International Gala for the '79 Washington International Horse Show.

A picture of sartorial splendor was Host True, who is really a True Host . . . ice cream pants, navy blazer, sharp tie and needlepoint slippers lovingly stitched by Steady Honey Judy Lewis.

True's house is a feast of aquamarine and cream and gold, good French furniture, gorgeous expensive clutter everywhere . . . stunning collections . . . and heroic silver pieces, which would be more than at home on Windsor Castle's Waterloo Banquet table.

Talking about his silver collection, True said with the resignation and surrender of a real collector . . . "Oh, lord, I'm just a whore about silver . . . I just plain love it and have bought it all over . . . England, France, Germany, Italy . . . the bigger and more ornate the better . . . I just love it, that's all!"

And that silver was holding another feast, the usual one served up when you drop by the Davis house . . . from the rarest of cheeses, fruits and delicacies in the dining room to hot dogs and burgers down by the Grecian-like pool, seemingly hanging in space on the hillside.

Two Margarets, Hodges, and Wimsatt, are chairing the gala, and they told all the plans afoot and how much money it was going to cost to be horsey this season. Everyone there knew that before the gala and show were over they were going to work and spend and seemed resigned.

Pledging up for same were the Joe Tydings; the Mandy Ourismans celebrating their 20th anniversary; Melody Gilsey in a Cher outfit; Judy McLennan in aqua silk evening pants and tunic saying she doesn't ride much now but works for the cause; Bill and Tina Fitzgerald; Saud Al-Soyawol, who has just added one half of Margaret Hodge's Jamaican house to his island holdings; Betty Mize; the Kiplingers, and terracefuls of others.

Hengst Wolf was at the gala planning to be sure everyone knew that his new Georgetown hotel, The Four Seasons, would be the site this year for the gala dinner and dance. Wolf is the manager of Washington's new hostelry, and is tickled his place was chosen for the Oct. 18 affair during horse show week.

To make sure all Hengst said about his hotel was true, several people went on to dinner there . . . Bette Quinn escorted by Bill Scott since the general was in New York on business . . . the Fitzgeralds, celebrating Tina's first outing since Baby Ashley came . . . Chris Kneib with super blonde Nancy Chemery . . . and Andy Parker.

The hotel is offering a gala doorprize of a weekend in a suite at The Seasons.

Chris Kneib, who is from the same part of Missouri as True Davis, and who is spending the summer doing good in the D.C. Public Defender's Office, spent his childhood in Tanzania on his family's huge coffee plantation, which they lost when the government nationalized all holdings of foreigners.

Chris' family now lives in La Jolla and he's in school out there, going back shortly. He told the greatest story of how his mother and sister were on a trip to North Africa, walking down a street in Morocco, when a passing limousine suddenly screamed to a halt and an Arabian in flowing garb got out. He approached Mrs. Kneib and her quite beautiful, blonde, fair daughter and on the spot made an offer of 100 camels in exchange for Miss Kneib.

Wise to the ways of the world, Mrs. K. somehow managed not to offend the sheik type, and forthwith hustled her beauteous daughter away before he could up his offer to an unrefusable number of camels!

Harry Belafonte, the originator of the open-shirt look, was in town this week . . . with the mayor and Effie entertaining him at a District Building reception, prior to which Harry urged the mayor and council to support the TransAfrica Lobby, for which he did his Tuesday concert.

The famous singer works with the lobby's head, Randall Robinson, supporting the organization's aims of hoping to influence the formation of a more liberal foreign policy toward African and Caribbean countries, communicating the views of black Americans to elected officials, the administration and the media.

The splendid five-story Dodge Mansion on Georgetown's P Street opened its portals to the American Theatre Association's committee planning their second International Theatre Costume Ball which will be held Sept. 29 at the Shoreham.

The host Tuesday night was the mansion's owner, Ricardo Garbacho, financial consultant, originally from Chile, whose uncle is the former Ambassador Puza of Chile. Ricardo has restored this historic house, which can boast some of the town's most interesting wrought iron, and he now haunts auctions finding just the exact right sort of period furnishings needed.

Rose Cowen, head of everything about the association and the ball, gave everyone their marching and dancing orders, with the evening ending in a buffet supper of Lucullan proportions.

Olga Esch heads the congressional ticket committee and is planning a luncheon at the 1925 F Street Club the day before for superstars and out-of-towners coming from N.Y. and Boston. Annette Perry of Upperville is helping Rose.

Don Peacock, who is party consultant on decor and stuff for the White House's Gretchen Poston, was enjoying supper with Baroness Garnett Stackleburg and telling of the scheduled art showing for his art work in London. His sponsor is Princess Aleah Kahn and her plans include a seated dinner and the show at the Savoy on Sept. 23.

Rumor has it that Princess Grace will follow up the London show with one for Don in Monaco in October. He's looking forward to being in the Principality, show or no show, for at that time he will be staying in his family's home there.

The costume ball's theme will be "All The World's a Stage" affording much choice in mad, gay attire.