"The only ones who didn't make it tonight," said National Theater board president Maurice Tobin, standing on the theater's stage last night, "were the bulldozers and the wrecking crew."

The performance of "A Chorus Line" had just concluded. But the 100 or so people still sitting in seats, perching on the edges of them or standing in the aisles for the after- show party applauded hard at Tobin's words. They knew how close the bulldozers had come, and they were now relishing the satisfaction of knowing that possibility had been averted.

The occasion was a party to celebrate the 143rd anniversary of a theater on the site of the National. It was also an opportunity to celebrate the fact that the theater had been saved. The Pennsylvania Avenue Development Corp. decided, after months of controversy, they would leave the theater standing.

And on top of that, the opening of the sparkly, witty musical (for a second time in Washington) was another thing to celebrate.

"It's good to see you have done this good thing," said actress Helen guests who included Livingston Biddle, chairman of the National Endowment for the Arts; Joseph Papp, producer of "A Chrous Line"; federal supporters of the arts and such Washington city officials as Mayor Walter Washington.

"Actors loved the acoustics of the National Theater,' Hayes said. "I remember in 1917 I played Pollyanna the Glad Girl. There must have been earlier times, but, uh..." she trailed off as the party guests chuckled.

Michael Austin, a cast member, agreed with Hayes' assessment, adding, "They're knocking down all the old theaters and building barns now. It's really a shame. The Kennedy Center is fine but we really need theaters like the National.It really gives actors and actresses a chance to see what it's like to perform in intimate theaters instead of to masses of people."

Mrs. Jouett Shouse, the builder of the Wolf Trap Farm Park for the Performing Arts, said the National is "a wonderful theater. We had another wonderful theater -- the Belasco, also near the White House. But they tore it down. I've always regretted that."

Out in the lobby, Tobin said that even the National Press Club, a nearby resident which originally supported razing of the theater, was now taking kindly to the thought of it remaining.

"They're still our neighbors," said Tobin. "No matter what happens, why not be neighborly?"