On a day when tournament coleader Nancy Lopez's game deserted her, Hollis Stacy, the defending champion playing in her ninth U.S. Women's Open at the age of 24, took the lead after the third round yesterday and immediately informed the world her nickname, "Spacey," no longer fits.

"I think those days are pretty much in the past, when some of the crazy things I did led writers to rhyme my name with something that sounded like it," she said.

"So," a reporter unquired, "what will you be doing tonight, to psych yourself up for the last round Sunday?"

The new Hollis Stacy thought a minute before answering, flashed her rosiest Savannah, Ga., smile, and replied: "What's your telephone number?"

Don't be misled.That answer was calculated for maximum exposure. Stacy is very much the one to beat as she attempts to become only the third player in history to score back-to-back victories in this prestigious even.

"I have (JoAnne) Carner. (Donna Caponi) Young and (Jane) Blalock in back of me. They're all veterans, all tough," Stacy declared. "It means I'm going to have to play aggressively - to be what I'd call 'aggressive conservative' if there is such a thing - and take on the golf course. Even par might be needed to hold the lead."

Stacy shot a one-over-par 72 yesterday for a 54-hole total of 217, four above regulation figures. Carner bogeyed the last hole for 73-218 while Blalock (71) and Young (73) continued in striking position at 219.

And what of Lopez, America's and ABC's sweetheart, for whom this tournament was to be just other four easy strolls around the course?

Don't ask. What was there to say after a 79?

"Thirty-five putts. Seven bogeys, one double bogey . . . and one birdie. That's the worst I've ever done as a pro in this country," Lopez acknowledged. "The only thing worse was an 81 in Japan last year.

The 14th hole was the "lowlight" of Lopez's play. Her drive ducked far to the right, into deep rough between trees. Her iron shot caught the trees, as she tried to punch back onto the fairway, the ball landing on the No. 5 tee box. She was still in the right rough after her third shot, from where she chipped 10 feet past the pin and two-putted.

"A 79 is really high. Horrible. I never give up. I make three birdies, they make three bogeys, and I'm back tied," Lopez suggested. "But 79! No one out here is supposed to do something like that."

Certainly not Nancy Lopez, who was tied for the lead with Donna Horton White and Carol Semple at the jalfway point Friday.

White, with 79, and Semple, with 77, did not stay near the lead very long, either. Semple, an amateur, finally played like one under the professional pressure.

But it was Lopez's poor effort that opened the door for Stacy and Carner. They lost little time taking advantage.

Stacy was exceptionally steady. She began with six pars before nailing a four-iron to within two feet of the pin on seven for a birdie. A two-iron over the green on nine gave that shot back to par, but she went into the lead again on 14 by chipping 25 feet uphill into the cup for a birdie with a pitching wedge.

Stacy was three shots ahead of Carner there, only to bogey 16 from a bunker and bogey 17 by blowing a three-foot putt.

Carner, winner of the 1971 and 1976 Opens, formed a twosome with Lopez and was a little lucky, at spots, to escape as smartly as she did. On the first hole, for example, Carner drove into the left rough and had to use a putter, left-handed, to get back onto the fairway. Her approach flew 50 feet past the pin - but she curled the long putt home for a par.

On five Carner again was fortunate after driving into the fight bank. She recovered with a four-iron shot that miraculously managed to reached the left edge of the green. Her string of pars finally ended on 11 when a seven iron caught a front bunker. Carner also bogeyed 15, missing a four-footer, then birdied 16 from six feet before "choking down" too much on a sand wedge approaching 18, leading to the bogey which cost her a share of the lead.

The 10th hole, a par 5 although only 450 yards long, is the best birdie possibility here. Lopez nearly knocked her drive out of bounds left. Carner went way right, playing a four-iron up the No. 1 fairway as her second shot.

It was that kind of afternoon as the third staight day of mid-90s temperature continued to take its toll. Peggy Conley, with a 70, and Kathy Martin, with 71, recorded the best rounds to join Semple at 221.

Neither of the Washington-area players who made the cut fared well yesterday. Mary ALick Caney came in at 77-229. That put them in close company, for one day at least with Lopez.