Tracy Austin, who will not be old enough to vote until a month after the 1980 presidential election, went to the White House yesterday.

Although she declined to say who would get her endorsement -- "I'm not going to get into anything political" -- she did give Amy Carter one of the tennis rackets that helped make her the youngest woman ever to win the U.S. Open.

"You can see it's been used," she said, standing in front of a fireplace in the "map room" on the first floor. "It's all worn out."

Austin, who said earlier that she was not nervous about going to the White House, had trouble deciding which racket to give the first daughter.

She was embarrassed that they looked so worn out, and worried that the strings might pop the first time Amy used it, until her mother reassured her that it was supposed to look that way.

Austin, who says she "is shy until you get to know me," relaxed visibly when she realized that Amy was even more shy.

The champ tried valiantly to make conversation. "Did you go to tennis camp this summer?" she asked (she had been told that Amy had).

"Yes," whispered Amy, "for two weeks."

"Do you use a one-handed, or a two-handed backhand?" Austin asked, perservering.

"Two," Amy allowed.

A public relations man came to Austin's rescue. "What's your favorite sport," he asked Amy.

She shrugged. "It must be tennis," he prompted.

"No," she replied.

Then these two blond children of the '70s were escorted into the diplomatic reception room where the White House press corps waited to record the moment for posterity.

The first preteen-ager and the first teen-ager of tennis have a lot more in common than a two-handed backhand. If Tracy Austin lives, at least part time, in a fish bowl, Amy Carter lives in an aquarium, Austin says she can identify.

"She's a little bit more famous," said Austin. "When I go home I have a normal life, I go out with my friends."

"She's more in the public eye," she added, moments later. "Every move she makes is taken down by the press. . . If she sneezes at the wrong time. . ."

Like Amy, Tracy Austin has grown up in the public eye. And that, she says, can be difficult.

"The public has seen her growing more than me. The public has seen me grow up, but just from 14 to 16. With her, they've seen her 7 to 12."

Make no mistake about it, Austin has grown up. She was in town to do a "public relations day," for the ColgateSeries Championship to be played at Capital Centre Jan. 2-7, and was asked about it during one of the "one on ones" with a local TV reporter.

"At 14, you were a thin little girl," he said. Now. . ."

Austin, eyes open wide began shaking one perfectly polished finger at the man. "Be careful," she said.

It was a long day -- 1 1/2 hours of practice, three television interviews, three newspaper interviews, a press conference, and the audience with Amy -- especially for a youngster with a cold.

Austin handled most of it like the pro she is (she has earned more than $300,000 in prize money so far), but there were reminders that she is still a child.

During one TV interview, she asked for a tissue. The cameras stopped. Tracy blew. When she finished, she looked up, not knowing what to do with the tissue. With no advice forthcoming, she crammed it between the pillow and the coach on which she sat.

Austin may not be overly sweet but she is not naive, either. When she arrived at the Potomac Tennis Club at 10:15 a.m. yesterday and found cameramen set up on the next court scouting out the best "photo opportunities," she firmly asked them to leave for half an hour.

They did.

Tracy Austin was a cover girl -- World Tennis -- by age 5. Sports Illustrated declared her a "phenom" at age 13 (her mother says only, "That made us realize she was unusal").

She was the kid with the braces and the bunches -- they are not pigtails, pigtails are braided -- and the little-girl pinafores.

She was cute.

But cute doesn't beat Chris Evert at the U.S. Open. Now people are talking about how tough Austin is. As in match tough, as in tough cookie.

"It's not tough," she said. "That's not the right word for me. "I'm not a big toughie. It's good concentration. Tough makes you seem so masculine."

When Chris Evert was 16, Austin's age, she was "Little Chrissie." when she began to win the big ones all the time, she became boring, mechanical, the Ice Maiden.

Perhaps that has already begun to happen. At a tournament in Minnesota last January, Austin had a strained hand. "The trainer said to ice it for 20 minutes," Austin's mother, Jeanne, recalled. "She had gone down to watch at the press table and a little kid came over and said, 'Can I have an autograph?' She said, 'I'm icing my hand, can I do it in a minute"'

"Some guy wrote that she was a brat who used a phony excuse not to give this sweet, adoring child an autograph. Well, why doesn't he check the facts? I felt like punching him in the nose.

"In America, there is a tendency to overexpose things," Jeanne Austin added. "They chew it up and spit it out."

How, she was asked, could she prepare her daughter for the moment when the infatuation dies, when a bored public, falls for someone new, say Andrea Jaeger (the new Illinois phenom)?"

"How can you?" she replied. "Chris told her, all of a sudden, they want the underdog."

"I've already come to that stage," said Austin. "Before I would lose in the second round and I was the underdog. There were a lot of girls who were better than me. Now I'm not the underdog 'cause I'm (No.) 3 in the world. I'd rather be where I am now.