It was an evening for celebrating all the way around. Nancy Thurmond's 35th birthday surprise party came on the heels of the Reagan administration's biggest congressional victory yet -- the go-ahead to sell AWACS to Saudi Arabia. And with all the Republicans and birthday cake around, it made for a very happy night.

"That was the finest vote that I've ever seen take place," drawled Sen. Strom Thurmond (R-S.C.), Nancy's husband. "And this little girl is the finest wife and mother I know. I usually can't keep surprises, but I kept this one for three weeks."

Nancy Thurmond thought she was going to a party for another couple and appeared genuinely surprised when Attorney General William French Smith, Secretary of Agriculture John Block, Sen. John Tower (R-Tex.), former representative and ambassador Clare Boothe Luce, Helga Orfila, wife of OAS Secretary-General Alejandro Orfila, and about 60 others all sang "Happy Birthday" as she walked in the door.

"I'm absolutely shocked," she said, blushing. "I had no idea. I'm so surprised."

"Isn't it wonderful to be 35?" chimed in the 78-year-old senator to much laughter. "It'd even be wonderful to be 45 . . . or 55 . . . or 65 . . . "

"Well, 35 really isn't the magic number tonight. It's 52," said Nancy Thurmond, referring to the number of senators who voted for the AWACS sale yesterday.

It was just about everyone's night, as high-spirited Republicans did a lot of handshaking and backslapping. "Thank you from the entire free world," Rep. Guy Vander Jagt (R-Mich.) yelled jokingly across the room to Sen. Alan Simpson (R-Wyo.).

Tower, chairman of the Senate Armed Services Committee, had just come from the White House, where, he said, "the president was very, very happy. I was over there with Sens. Howard Baker, Chuck Percy, Paul Laxalt and John Warner . . . Reagan was in a fine mood."

"I'll tell ya," said Lee Atwater, special assistant to the president, "the best thing that guy has going for him is himself. The president pulled the election out by himself, and he pulled this out by himself. He's amazing. I was with him the other night when he first realized he had the votes. He's mighty happy tonight."

Doug and Mary Jo Campbell, close friends of the Thurmonds and hosts of the party, were also mighty happy. Think how sad everyone at the Northwest Washington home could have been. Doug Campbell, another South Carolinian, is a special assistant to Energy Secretary James Edwards.

Guests trickled in and out of the balloon-and-flower-bedecked house, biting into shrimp, chicken, shish kebab and a two-tiered birthday cake decorated with tiny American flags.

Nancy Thurmond blew out all 35 candles. Senate See THURMOND, B9, Col. 1 THURMOND, From B1 wives generally recover from surprises quickly, particularly those who might some day run for their husbands' seats. Nancy Thurmond regained composure and charmed the throng of politicians, socialites and diplomats gathered.

"We generally just celebrate Strom's birthday," she said, referring to her husband, who is often the brunt of jokes about age. "Then our children get to blow out the exact number 78 of candles." Everyone laughed.

In addition to Nancy Thurmond and AWACS, there was one more hit of the party -- 4-month-old Lilly Stevens -- daughter of Sen. Ted Stevens (R-Alaska).

"We take take her everywhere we go," said Stevens, as everyone tickled and made baby noises in front of her. "Her mother is the restaurant, so she's got to go everywhere we go."

Then little Lilly let out a whopper of a wail and out the door the Stevenses went.

By 8:30 p.m., they were followed by most of the party. Everyone had the same date to keep.

"I've got to go," said Attorney General Smith, fingering his watch. "I can't miss the World Series. Aren't you going to watch it?"

"Oh, sure," said Secretary Block, "I'm for the Dodgers. How about you?"

"Well, they're my home team," smiled Smith, edging out the door. "They're going to win. It's been a good day."