The humidity was fierce enough to wilt 100 hairdos and stain as many tuxedos, but Washington being Washington, an astonishing portion of the government that matters was there. "Are you kidding?" said Reagan intimate Nancy Reynolds, wearing a long blue dress and blue suede cowboy boots. "This is a double-header."

In one part of the green-striped party tent, quite literally pitched at the foot of the nation's Capitol, was public-relations man, inaugural co-chairman and Republican insider Robert Keith Gray, host of the evening. In another part was Sen. Paul Laxalt (R-Nev.), guest of honor because he helped elect Reagan. Laxalt is the former co-chairman of the Reagan-Bush campaign and the president's closest friend in elective office. In this town, that translates directly into power. A party in his honor -- you show.

"I saw the guest list this afternoon," said Laxalt. "It was unreal." He's the man who once said, "If there is a perception of power, that is the greatest power."

Here's who showed:

The White House Big Three -- Edwin Meese, James Baker, Michael Deaver. Nine Cabinet members, including Secretary of State Alexander Haig and Attorney General William French Smith. Thirteen House and Senate members. Richard Allen, the national security adviser. Katharine Graham, chairman of the board of The Washington Post Co. Columnist George Will. White House decorator Ted Graber. Woman-about-town Anna Chennault. Entertainers Donny and Marie Osmond. And Richard Viguerie, the right-wing prince of direct-mail politics.

Viguerie already has had plenty to say about Reagan's nominaton of Arizona Judge Sandra O'Connor to the Supreme Court, but last night, when slightly prodded, he began again. He thinks O'Connor is too liberal on social issues, particularly abortion. And lots of liberals have backed her.

"When you've got Ted Kennedy, Tip O'Neill and Alan Cranston saying this is great, somebody's got something wrong," Viguerie said. "I'm clearing my schedule for the next several months, and I'm going to devote the lion's share ot it to this project -- to urging the president to withdraw the nomination."

Most in the crowd, a sizable part of the Ronald Reagan political fan club, had nothing but praise for the nomination.

Sen. Strom Thurmond (R-S.C.), chairman of the key Senate Judiciary Committee: "I'm going to support the nomination, unless something unexpected comes up in the hearings." He didn't say what.

Martin Anderson, White House domestic policy adviser: "The president had been thinking about this a long time. No one believed him, no one believed a lot of the things he had to say."

A senior White House adviser who didn't want to be identified, speaking about the right-wing opposition to O'Connor: "It may not be all that bad, from a purely political standpoint, to have a fringe element out there.It puts to rest any claims that Ronald Reagan is an extremist."

The party began in a swampy haze, the sun hanging like a lump beside the Washington Monument. As the 200 partygoers arrived at the tent pitched on the grass beside the Capitol reflecting pool, sweating joggers and fascinated tourists stopped to stare at another curious part of the capital's political and social culture.

It was unbelievably hot.

"When you run the government," observed George Will, "I don't know why you can't get the army to fly helicopters overhead and stir up air."

By dinner, there was relief: a summer eye's breeze, and then dessert, on two buffet tables with silver candelabras. They were just a few feet away from the reflecting pool and the lights of the Capitol.

White House Chief of Staff James Baker stood near one candelabra, cigar and brandy in hand, Texas Rough Outs on feet. (The invitation, requiring black tie, read "Boots Optional.")

Baker, who ran Gerald Ford's '76 campaign the year that Laxalt ran Reagan's, just plain likes the guy. "Those of us in the administration aren't here because of Paul Laxalt's power," he said. "We like Paul Laxalt. And it's a good party. Now there may be some people here who. . ." lHe stopped, thinking better of continuing. "But not the administration people."

The site for the party was Gray's idea. First he had to get permission from the U.S. Park Service, then the architect of the Capitol. Next he had to have a water tank on the premises, a bathroom tent and an electric generator to operate the fans and white Christmas tree lights on the trees overhanging the tables.

"A typically simple and modest Bob Gray party," observed Laxalt dryly.

Gray, a Washington fixture who recently left the Hill & Knowlton public relations firm to form his own Gray & Co., wouldn't say how much the Bob Gray party cost. "Oh," he said, "everything in life is expensive."

One party highlight occurred when Gray presented Laxalt with a $1,000 check. It was the beginning, Gray said, of a $25,000 fund that will pay for an elephant at the National Zoo -- named Paul. Then Laxalt, the son of a Basque sheepherder, presented Gray with a traditional Basque hat.

There were actually a few old Jimmy Carter Democrats at this Republican fest: Anne Wexler, a former presidential assistant, and Stuart Eizenstate, the former domestic policy adviser. He was talking to Martin Anderson, his Reagan administration counterpart.

"Come on over and let's have lunch," Anderrson said to Eizenstat. "Let's see if I can explain how these Cabinet councils work."

"How do they work? one skeptical guest inquired.

"They work very well," responded Anderson seriously.

Anderson's wife Annelise, who works at the Office of Management and Budget, burst out laughing.