Nathan Landow went national this weekend. And who, might ask, is Nathan Landow?

Well, Nathan Landow is a rich Maryland real estate developer who, way back when Bella Abzug was running for mayor of New York City, helped fill her campaign coffers.

And Saturday night it all paid off, at least in media coverage, when Barbara and Nathan Landow welcomed to their Bethesda jome not only Abzug but her best buddy Shirley MacLaine and her "Turning Point" entourage.

As dinner parties go, it had almost as many reporters as it had guests. And although the RSVPs from the White House crowd had been high, according to one insider, the heavies didn't show.

Not that MacLaine minded. Those who were there - Jerry Rafshoon, Pat Caddell, Midge Costanza, Richard Harden, et al - were all staunch supporters of the actress since the campaign.

MacLaine's co-stars in the film, Anne Bancroft and Mikhail Baryshnkov, weren't there either, but Bancroft is appearing in "Golda" on Broadway, and nobody seemed to miss Baryshnikov, anyway.

"Turning Point" director Herbert Ross, executive producer and former ballerina Nora Kaye (who is also Ross' wife), screenwriter and co-producer Arthur Laurents and the film's ingenue ballerina, Leslie Browne, showed up, however.

Browne, now with American Ballet Theater, said she liked show business just fine even though if forced to choose, ballet would still come first.

In fact, ballet is so much her first love that Browne, cast in the film as a young ballerina who falls in love with Baryshnikov, said their on-screen romance stopped there. On screen.

"Absolutely not," she said at the party, a sentiment she dittoed again yesterday at a Watergate brunch for some of the film's principals. "No, we're just colleagues."

Baryshnikov, or "Misha," as she calls him, gives few compliments to dancing partners. "He gives a small amount of encouragement. He may say 'not bad' but he never says something was 'good'."

Dressed in a romantic if somewhat bizarre-looking black net off-the-shoulder gown, Browne wandered around the party looking somewhat lost in the mix of politicos, show folk and what was said to be a heavy representation of big-monied Democrats.

By the time MacLaine and entourage, including Bella and Martin Abzug and New York magazine editor Joe Armstrong, arrived, guests had been serenaded for an hour by a live quartet. Bella said she had no idea if this was a typical Washington party because, "I've never been to one down here in a house before. I mean, I've come down for political dinners but that's about i."

For Costanza, it was a rare night out and she found herself the center of attention from those sympathizers who were displeases by Newsweek's recent story about her. Her own reaction, she said, had been to ask the President for 15 minutes of his time and to get, instead, and hour and 10 minutes of it.

"We had the most wonderful talk," she said. "He said, 'Midge, don't feel badly about it. Have you read my press lately'"

Harden, special assistant to the President, said he was not the least bit worried about the negative Carter press. "Listen, I was with Jimmy when he was governor and for four years we didn't get one nice word out of Reg Murphy at the Atlanta Constitution. Hah, this is nothing."

After the buffet supper, the 85-year-old Las Vegas hypnotist and magician Jimmy Grippo, who flew in for the "Turning Point" weekend, dazzled guests for nearly four hours with his card tricks.At one point, touching Costanza's fingertips in a way that was intended to produce a reaction from her, she reacted with some surprise, "I think I've reacted."

"First time in a year," razzed Shirly MacLaine.

Yesterday, at the Watergate brunch, MacLaine wasn't there but Baryshnikoy was for a while at least, and so were Ross, Kaye, Laurents and Borwne.

Coincidence, yes, that ingenue Browne should play ingenue Emilia, the role in "The Turning Point" that Gelsey Kirkland would have filled had not illness forced out, according to Ross.