"This is Harry's party tonight, and I'm here for Harry," said Joseph Papp, standing, hands on his hips and tuxedo jacket open, in the middle of a living room whose owner had just commanded everyone to be seated on the floor.

Harry was Harry Bagdasian, founder and director of New Playwrights Theatre, and Joseph Papp is the New York producer who brought you "Chorus Line," the man who brought Central Park free Shakespeare.

Papp stood in the middle of the living room proclaiming that Bagdasian was a success and that what he was doing was not only important to theater in Washington but to theater in America -- clearly, that should have been Harry Bagdasian's finest moment.

"Well, he's a little sick now," said Papp in a hushed tone, his face mock-sober, as he looked across the room later at Bagdasian -- a slightly stocky Al Pacino look-alike in tuxedo.

"It's psychosomatic," Papp explained. "I just said to him, 'Harry, didn't you get sick the last time you had something big to go to?' He's a nice man. . . ."

It was a benefit and dinner (at $50) for the New Playwrights Theatre, which devotes itself rather successfully to the works of new playwrights. And last night was its coming-out party -- its debut after seven years into the Washington society of heavy-duty partons, where people come in black tie and lots of makeup and ask about the origins of the art on the wall.

"We're trying to introduce new Playwrights to an audience that isn't familiar with us, that normally goes to the Kennedy Center or Arena," said board member John Goodman. "We've been basically for young professionals."

And there were those around last night -- along with lots of board members from the National Theater, and guests like Patrick Hayes, director of the Washington Performing Arts Society, and Democratic Party fundraiser Esther Coopersmith, and Livingston Biddle, chairman of the National Endowment for the Arts, and Richard Helms former director of the CIA, and Smith and Vicki Bagley.

Otherwise, Joe Papp was the main guest and almost everyone -- including reporters -- ferreted him out as he wandered through the intertwining rooms of the Northwest home of Roland and Meredith Homet (Roland is a New Playwrights board member).

"This is rare," said Papp about New Playwrights. "Most theaters do old and tired plays." Papp first saw a New Playwrights performance -- of Ernie Joselovitz's "Hagar's Children" -- on Dec. 10, 1976 (Bagdasian remembers these things).

"He came on the last night, and afterwards, he said he wanted to see the cast," said Bagdasian. "He told them, "This is a moving play and I want to keep it going. I don't want to change a thing.' Our mouths fell open. Then he said, 'Anybody who wants to do plays like this, put me on the board.'"

Among the current Papp projects is the repertory theater that he is planning in collaboration with the Kennedy Center's Roger Stevens, which will open for five weeks of repertory in March of 1981, Papp said last night.

"We're negotiating with Meryl Streep, Robert deNiro, Raul Julia, Jon Voight, John Heard, Roscoe Lee Brown, James Earl Jones," said Papp. "We're talking with Al Pacino. The response to this is fantatic. There's nobody I can't get. There's nobody who won't say yes."

He stopped for a moment. "That's wrong. That makes me sound omnipotent."