Favored Nancy Lopez provided the disappointment and little-known Judy Clark threw in the drama, but a cold-eyed youngster named Kathy Baker quietly stole the lead today in the 40th U.S. Women's Open at Baltusrol Country Club.

Baker's four-under-par 68 gave her a 54-hole total of 210 going into Sunday's final round. Clark, a veteran nonwinner on the LPGA Tour, and Lopez, who never has won an Open, were one stroke back.

Lopez, troubled by ill luck on the greens, watched several birdie opportunities run around the hole on her way to a 71. It was a somewhat disheartening round on a day when the rest of the field was wreaking havoc at the rain-softened Upper Course at Baltusrol that gave up several records.

Foremost among them was that set by Clark, who shot a nine-birdie, seven-under-par 65 to tie the U.S. Women's Open mark for lowest round. It also was a course record.

Other records set were for the most subpar rounds in a single day at an Open, and also for an entire championship. Sixteen players broke par, the third time in three days that record has been rewritten, and 37 subpar rounds have been recorded, breaking the previous mark of 33, set in 1981 at La Grange Country Club in Illinois.

Two strokes behind Baker were Vicki Alvarez and Janet Coles, two little-known players who had been tied for second after Friday's round. Each shot 71 today.

Their presence meant that Lopez, despite her relatively staid round of two birdies and one bogey, is the only player among the five leaders who has won an LPGA tournament and is ranked in the top 10 money winners. Although it was the first time this week that Lopez has given up a share of the lead, she is still considered the favorite.

"Being behind is fine," she said. "I've won most of my tournaments from behind."

Baker, a nervy 23-year-old former NCAA champion from the University of Tulsa, had an unbroken string of pars on the front nine before birdieing five back-nine holes. Her last one came on the par-4 18th, a 25-foot putt that went straight for the heart of the hole.

With the putt, she reclaimed the lead she had lost with her only bogey -- on the par-5 17th, when she hit a wedge into a bunker. Her other birdies came on the par-3 10th, par-5 11th and par-3 15th -- all with eight-foot putts -- and the par-4 15th, where she sank a 25-footer.

Baker, described by ABC analyst Dave Marr as "Jane Fonda's kid sister," has a history of playing well in the Open. She was the low amateur in the 1981 and 1982 tournaments, and has been almost irritatingly unimpressed by her surroundings this week.

"I'm not going to say, 'Uh-oh, this is the Open,' " said Baker, who is in her second year on the tour. "I'm just looking at tomorrow as another day. It's 18 more holes and then it's over."

Clark's birdie-strewn round tied Sally Little's record of 65 set in 1978 in the final round at Indianapolis Country Club. But Little's mark was a six-under-par round set on a par-71 course, technically making Clark's seven-under performance the best round ever. It also broke the record for third-round score in an Open. The previous record was set by Judy Bell, an amateur who shot a 67 at the 1964 Open in San Diego.

"This is so great, when you do it right," Clark said. "I can't describe what it's like to play that well. It's what it's all about."

Clark came from six strokes back after shooting a 75 Friday for a 36-hole total of 146. She birdied four of the first six holes, generally acknowledged to be the toughest of the course, had three more sub-par holes at nine, 10 and 11, and then birdied the 16th and 18th holes, the last with a curling, 25-foot putt.

"Oh boy, was that fun," she said.

Her two bogeys came on the third and 17th holes. At the par-5 17th, apparently still affected by the crowd's roar for her eight-foot birdie on 16, she topped a three-wood from the fairway that caught the lip of a bunker and died.

"It was my one dumb shot of the day," she said.

Clark never has won a tournament in seven LPGA seasons, and the conventional wisdom here says that a nonwinner cannot claim this title on this course, the toughest the women play all year. But she is experiencing the best season of her career, with eight top-10 finishes to rank 13th on the money list with $88,306.

Lopez, playing in the final twosome with Coles, was well aware of what was happening on the course ahead of her, but seemed incapable of doing anything about it. Her birdies came at the par-3 third, with a six-foot putt, and the par-4 12th, where she sank a 25-footer. Her lone bogey came on the 13th, where she three-putted from 15 feet.

"It was real noisy today," she said. "I could hear it in front of me so I knew something was going on. I was disappointed I didn't get more out of the round. The putts just lipped out, they looked like slow motion. I was hitting them well, and I felt like I just had to be patient and they would start going in, but they didn't."

Among her near misses were a six-footer on the first hole, a 20-footer that seemed aimed directly at the hole on the sixth, a five-footer on the eighth that ran around the cup, a 10-footer on the ninth, a six-footer on the 11th and a 12-footer on the 15th.

"Hopefully, everybody got the birdies out of their system," she said. "I always say I'll take a 65 on the last day."