Anyone who has ever had a glimmer of affection for golf owes it to himself to watch the final 18 holes of the 83rd U.S. Open from Oakmont Country Club Sunday.

For that matter, anyone with a taste for natural drama, the galvanizing sort of real-life event that art can't duplicate, should not ignore the potential of this day (WJLA-TV-7, 2:30 p.m.). The stage was set so perfectly here this afternoon that it will take considerable ill fortune to prevent this Open from reaching a splendid climax.

Tied for the lead in golf's premiere tournament are the two greatest players of the day, Tom Watson (70 today) and Seve Ballesteros (69), at one under par (212) after three rounds. They hold the wishbone of contemporary golf between them and both are pulling with one thought.

Only one stroke behind are Calvin Peete (70), one of the most compelling underdogs in the history of golf, and Larry Nelson, who, after an 18-month putting slump, drained everything today for a startling 65. As though that weren't sufficient, the fellow alone at 214 is flamboyant reformed playboy Raymond Floyd (72), ol' Tempo Raymondo, who at the age of 40 wants to win the Open title that has eluded him for 20 seasons.

And only a breath behind those worthies are sedate Gil Morgan (70--215), rising young Hal Sutton (73--216) and former Open champ Andy North (72--216).

Golf seldom has had a final round that insisted so loudly on its thematic potential.

Watson could become the first player since Ben Hogan in 1950-1951 to win consecutive U.S. Opens. Peete could become the first black man to win a major golf championship. And, with a victory, current Masters champion Ballesteros would be halfway to the Grand Slam.

Most central is the struggle between coleaders Watson and Ballesteros, who played almost flawlessly today. From the third through the 17th holes, Watson hit every green in regulation. Ballesteros, known for only one weakness, wildness off the tee, hit all but one fairway today.

These two are at the peak of their mighty games. Ballesteros is golf's most titanic hitter, its most spectacular escape artist and one of its hottest streak putters. Watson is almost as long, almost as daring, a better tactician and manager of his own temper, and, probably, the best putter, long range or short, on earth.

Both say they're hot and expect to win.

"I played very consistent today," said Ballesteros, prospering with a new conservative game plan that has him hitting one-irons off 11 tees. "I was in the rough just once. A good record for a little Spaniard, no? . . . Perhaps I will continue to be lucky (on Sunday)."

"My putting was exceptional today," said Watson, who has hit more greens and had fewer over-par holes (six) than any player here. "Because I won (the Open) last year, I think I'll be more relaxed this time . . . You know me, I love competition. Sometimes I need a rude slap in the face to get things done."

Two months ago at the Masters, this pair played together in the final round and began an inspired and cordial argument over which should rule the sport now that the king of kings, Jack Nicklaus, seems finally to have grown old. That April day, Ballesteros began birdie-eagle-par-birdie and swept to victory, leaving Watson in fourth place.

It took the tenacious and high-strung Watson 10 years to win his first Open. It was the title that eluded him, tormented him and delayed his ascension to the game's throne in the public mind. Last June, Watson outdueled Nicklaus in what may, in time, prove to have been Nicklaus' last great stand. Now, Watson, who bogeyed the 18th this evening to fall out of the lead, must face the fresh challenge of Ballesteros.

And, Peete is only a stroke behind them, in pressureless position; he has no lead to blow, yet the minimum number of strokes to make up.

"This course here is my best chance to win the U.S. Open. Of the courses we play, and that I hear we will play, I think I have the best chance here," said Peete.

Asked if being the first black man to win the U.S. Open would have any special meaning to him, Peete replied, "That wouldn't make any difference. Just to be the winner of the 83rd U.S. Open would be enough."

Peete, who never touched a club until he was 23 but who has spent the last 17 years mastering his utterly idiosyncratic, self-taught swing, played his second consecutive splendid round this afternoon. He teed off at 7 a.m. and played the last hole of his rain-delayed second round, which he bogeyed, to complete a 68. Then, after going back to bed until noon, Peete returned to Oakmont and played bogeyless golf until the final hole when, for the second time of the day, he took 5 at 18.

Going into the final round, the hot hand belongs to Nelson, who won the 1981 PGA, but has, in the last year, become perhaps the most abysmal putter on the PGA Tour. This year, Nelson, a marvelously straight and long driver, has been fourth in hitting greens in regulation, but because of his nightmare putting (158th on tour) is 102nd in scoring and 92nd in money won. "I got so I couldn't even make the four-footers," said Nelson this week.

Today, he made everything, playing 11 consecutive holes (five through 15) seven under par, making birdie putts of 3, 10, 25, 1, 25, 15 and 6 feet. Nelson bogeyed the third and 16th, but finished with a seven-foot birdie putt at the 18th. He should sleep well, knowing that his new putting method (hold the club up off the ground, never sole it) is fresh in mind.

Beware of a proven player with a new gimmick-swing thought.

Floyd ended the day exasperated over a blown birdie chance at the 15th and a bogey at the 16th. Nonetheless, he loves this just-off-the-lead position; this week has mirrored the invisible-'til-the-end manner in which he won the 1981 TPC which brought him $322,000 in prize money and bonuses. Floyd loves a high stakes game, is nerveless under pressure and may be due for his round in the 60s for the week.

Since Peete seldom makes a putt over six feet anyway, it should hurt him least if everybody gets the normal case of Open panic on the homeward nine. If lots of sweet-swinging regulation pars are enough for victory, Peete could find himself one of the best-known figures not just in golf, but in all of American sports. Watson and Ballesteros could win a golf tournament, but Peete could win a place in his nation's sociological history.

Normally, Peete is one of the shortest drivers in any PGA Tour event. This week, by a twist of fate, he may actually be the longest driver in the field.

In locker room parlance, everybody else here is afraid to take his "big dog" out of the bag and let it eat; they're leaving the furniture (woods) in the sack.

Ballesteros hits woods only three times per round, while Watson used only five woods off the tee today. Peete is so preternaturally straight, however, that he uses his driver 11 times in each round, his three-wood twice and only goes to a one-iron off the tee on the tiny 322-yard 17th.

For the first, and perhaps only time in his career, Peete actually has the shortest shots into the hole, not the longest.

Despite using his driver so much, Peete leads the entire field in hitting fairways (82 percent).

The tough guy, however, may be the holder, Watson. Once, he eroded his own confidence with esoteric talk about whether his swing was in sync. Now he says, "You can't think about your swing and think about scoring at the same time. You just go out with what you have and shoot a score."

A week ago, Watson said in a phone interview, "I'm playing like a 4-handicapper." On Tuesday, he told a close friend of the family that he thought he had little chance in the Open because he had played poorly, by his standards, all season.

Now, suddenly, his game gets sharper every day. Did he just will himself to play well? "That seems to be about it--will power," he said with a shrug.

This afternoon, both Watson and Ballesteros made a half-dozen tough par putts in the four- to eight-foot range. Neither would crack first. "That's hard on the nerves," said Watson. "Once you start missin' those, then you keep missing 'em . . .

"It's been like a chess game all week. Everybody has been getting their army into position."

Seldom has the final battle of a golfing war been awaited with more cheerful anticipation.