Two years ago, Nancy Lopez, a 21-year-old rookie from New Mexico, came to the Greater Baltimore Golf Classic and began a string of five tournament victories that would dazzle the world of women's professional golf like nothing else in its history.

Midway through the LPGA tour that year, Lopez was hailed in sports columns and newscasts as the Moses who would lead women's golf out of the wilderness of obscurity into the promised land of network television and nationwide publicity.

Sports Illustrated put her on its cover and she became the first LPGA golfer to be named player-of-the-year and rookie-of-the-year in the same season. Into the 1979 season the pace continued, and by the end of that year Lopez, by then married and known as Lopez Melton, had won 17 of 50 tournaments and earned $410,.440.

Women's golf, it appeared, had at last found a superstar.

This week, Lopez returned to Pine Ridge golf course, on a jovely lake just north of Baltimore, seeking, at the age of 23, to recapture the form and the glory of her youth.

"I didn't practice over the winter," she said. "And when I came back on the tour, my swing was flat."

By ordinary LPGA standards, 1980 has not been a bad year for Lopez. Going into the greater Baltimore Classic, she had won two tournaments, the Women's Kemper Open and the Sarah Coventry. Winnings of $104,000 put her in third place behind Amy Alcott and Donna Caponi Young.

By Lopez's standards, 1980 has been a bad year.

"It's been a tough year for me, so far," she said. "First, I was having problems with my swing, and then I started having mental problems. After the first two years, I was under a lot of pressure, and I started losing my confidence."

To fall into a slump after a stunningly successful beginning is a story as old as the history of professional sports. But for Lopez, the implications extend beyond her own athletic career to the entire LPGA tour.

For the record, LPGA officials insist the 1980 tour is bigger and better than ever before.

There are more tounaments -- 39; more dollars in prize money -- $5 million; more television dates -- 16, and more $100,000-plus purses -- 39 -- than ever before in the 30 years of the LPGA. Galleries continue to grow, and since 1975 there has been a 317 percent increase in the dollar amount of the purses.

It also remains a fact that without Lopez playing at her peak, the tour has somehow lacked the drama and excitement of 1978 and 1979. No other women golfer in recent years has stirred the enthusiasm of fans or generated the crowds that Lopez has.

Even in an offyear, she remains the favorite of the crowds.

"This is where I started my streak two years ago," she said between holes of the pro-am tournament Thursday preceding the Greater Baltimore Classic.

I'd like to do it again."

'Nancy," counseled an elderly woman from the crowd, taking Lopez gently by the arm. "You're GOING to win. And it's nice to have you back."

Growing up in Rosewell, N.M., Lopez learned golf from her father Domingo Lopez, owner of an auto body shop and an avid amateur golfer.As a child, she was not allowed to wash dishes on the grounds that her hands were meant to be wrapped around golf clubs, not dishrags.

At the age of 12, she amazed the golfing community by winning the New Mexico Women's Amateur championship, a feat she would repeat twice. Later attending the University of Tulsa on a golfing scholarship, Lopez won the AIAW national collegiate title and four other tournaments before turning professional.

Just this week, the All American Collegiate Golf Foundation announced that Lopez next month will become the first woman golfer in its hall of fame.

"Nancy Lopez has done for women's golf in the 1970s and '80s what Arnold Palmer did for men's golf in the 1950s and '60s," said William D. Fugazy, the foundation general chairman.

In pretournament play last week at Pine Ridge, Lopez said she could feel her swing coming back, but it had been a struggle.

Returning to the tour after a two-month vacation with her husband, Tim Melton, a Cincinnati sportscaster, Lopez discovered something that happened to her swing.

She wasn't sure what was wrong. "The problem is I don't have a teacher, and nobody was watching my swing," she said.

Eventually, her caddy and her daddy, both of whom serve as unofficial coaches and mentors, diagnosed the problem: a troublesome flatness. Lopez took a week off to work on it, then returned to the tour. Since then, she says, progress has been slow but steady.

"I feel like I'm hitting the ball well now," she said. "And I've regained my confidence."

Two years ago, when she began her five-tournament blitz at Pine Ridge, Lopez recalled, she already had won two tournaments.

"It's the same this year," she said. "I've won two tournaments so far. Maybe. . . . ."