At sundown today, the clouds above Watchung Mountain finally burst and shed their rain on Baltusrol Golf Club.

That downpour at dusk was like the bursting of an emotional dam that had borne ever more weight here for four days as Jack Nicklaus struggled with himself to win his fourth U.S. Open championship.

This 80th Open was a rack straining the nerves and tormenting the sentiments of thousands of Golden Bear fancieers, some of whom hung from trees and howled to the heavens here, pleading with their long-slumping hero to reclaim his golf majesty.

Finally, on the final nine holes of this dramatic Sunday round, Nicklaus released that tension with an explosion of some of the most nearly perfect golf of his unmatched career.

With a grand birdie-birdie finale, Nicklaus shot a two-under-par 35-33 -- 68 to set an Open scoring record by three shots with 63-71-70-68 -- 272.

In any other Open in history, Japan's Isao Aoki would have taken first prize with his 68-68-68-70 -- 274. All he got, after four rounds of head-to-head dueling with Nicklaus over Lower Baltusrol's 7,706 yards, was second place by two shots over the vaunted Tom Watson and two others -- and what he called "The great lesson of playing with the greatest golfer in history."

At his victory ceremony, Nicklaus, normally polished and almost glib, was at a befitting loss for words "I don't know where to start," he told the crowd that now adores him as much as it resisted him when he won the Open from Arnold Palmer when it was last played here in 1967.

"If you don't mind," Nicklaus said, "I'm just going to stand here and enjoy this."

And he did. He stood so still for so long, simply gazing out at the crowd and the mountain in silence with a beatific smile on his face, that the throng spontaneously broke into applause.

Nicklaus was eloquent with more than his silence, with more than his golf clubs.

"I have to start with self-doubt," said Nicklaus, always the man of self-knowledge, self-criticism, even in the hour when he had played one of his most sublimely confident rounds.

"I kept wondering all week when my wheels would come off like they have for the last year and a half," said Nicklaus, who, after driving into the rough at the sixth, seventh and eighth played flawless golf the last 10 holes. "But they never came off. When I needed a crucial putt, or needed to call on myself for a good shot, I did it, And for a good shot, I did it. And those are the things I have expected from myself for 20 years.

"I've wondered for the last year and a half if I should still be playing this silly game," admitted Nicklaus, who now has 18 major golf championships. "I wondered if by playing I was being fair to the game, to my family or even to myself.

"If I wanted to go out with all the dramatics, I'd probably say goodbye to golf today.

"But I'm not going to retire. Maybe I should, but I don't have that much sense. I'm serious when I say that maybe I should. But I still think this old body has a few more wins in it."

Nicklaus' most bitter disapointment, as he fell to 71st in money winnings in 1979 and humiliated himself with uncharacteristic collapses many times, was the haunting notion that he had, in some deep inner sense, lost contact with himself.

"You see guys who have been winners who get to the point where they ought to get out of their game," said Nicklaus, after shooting the second-best round of the day -- and the only under-par round today by any of the genuine contenders. "They are the last to know. They make themselves seem pathetic. It hurts to think that that is you."

After this afternoon of theatrics, Nicklaus should have golf sustenance to feed on for several years.

All around him, the young and strong were falling apart.

Watson drove wildly off the first tee, made a bogey, and never got close to threatening position as he carded 70 and finished tied for third at 276 with Lon Hinkle (71) and Keith Fergus (70). In fact, only Aoki and those three finished this Open under par -- that is to say, fewer than eight shots behind Nicklaus.

Only Aoki proved to have the staying power to push Nicklaus until the very end.

The 37-year-old Aoki, who never has accomplished anything outside Japan that remotely approached his showing here, was overly modest, saying, "It's finally finished. It's over. . . . On the front nine, I felt the pressure of the U.S. Open. It kind of worked on me. I just wanted to hang on to Nicklaus more than I wanted to win. I never really offered him a challenge."

Only half true.

Aoki did look exhuasted early in the round. And he did back out of his third-round tie for the lead with Nicklaus by bogeying four of the first nine holes. His putter, which set an unofficial Open record of 112 strokes in 72 holes (breaking Billy Casper's mark of 113 in 1959), betrayed him completely in that stretch. He looked woebegone and beaten.

After his only three putt performance of the Open at the second hole, Aoki missed six consecutive makable putts of four to 12 feet on the front nine as Nicklaus took that two-stroke lead.

However, to Aoki's credit when Nicklaus became inspired on the final nine, so did the Oriental wizard, turning in an identical card for the back with birdies at 10, 17 and 18.

This Open lacked on moment -- one shot -- of crunching drama. However, two situations on the back nine will remain in Nicklaus's mind -- once when he resisted the possibility of letting those wheels come off, and once when he rose to a great occasion.

At the 10th, Nicklaus slammed a seven-iron shot a yard from the hole on the 454-yard par 4 for a seemingly certain birdie. Aoki was in the fringe with a tough chip.

"You know," Nicklaus said to his caddie, "I bet he holes this."

Aoki did, for a stunning birdie that cut Nicklaus' lead to one shot.

As Nicklaus prepared to putt, a boozy voice from 50 feet away, beyond the circle of the green, bellowed out. "Aaaaeeeee; Kamikaze!"

A Nicklaus fan yelled back, "Jack's the best!"

The anonymous voice cut through the green side silence with an obscenity. An even deeper nervous silence fell.

Nicklaus badly needed the three-foot birdie putt. His wheels had wobbled at No. 6-7-8 on those wild drives. Twice he saved par and once took bogey. And he was worried. After the last of the erratic tee balls, he moaned to his caddy, "Angelo. I can't find the fairway."

Now, at the 10th, Nicklaus took the putter head back. And just at midstroke the idiotic voice cut through the air at full volume screaming "Aaaaee, Kamikaze." The voice was that of an American and the face that went with it, too. Likely not an Aoki fan, but another of those Nicklaus haters that this man thought he had left behind with his fat and his short hair and Arnie's Army.

Somehow, Nicklaus backed off in midputt. The crowd was ready for an impromptu lynching. "That's all right," Nicklaus said firmly to the crowd, putting up his hand in a gesture of peacemaking.

But Nicklaus was rattled. As he stepped away, he fumbled his putter to the ground, bent over, and muttered to himself, "I guess."

On Friday, when he had a five-shot lead, Nicklaus backed off a three-footer after hearing a helicopter. He missed. His wheels came off for the rest of the day (three over thereafter) and his lead evaporated.

This time he sank the putt. His lead was two shots. And that's where it stayed all the way to the clubhouse.

"I played as good a nine holes on the back as I ever have in my life," said Nicklaus. "But I didn't think I had won until I made birdie at the 17th."

At that instant, Aoki, the specialist at match play, was, in a sense, "closed out" since he trailed by three shots.

Aoki then ran home a 10-footer for his birdie at 17, and, following Nicklaus' birdie on the final hole, tapped in a three-footer there for another. No one will ever know if he could have made those final birdies if the stakes heretofore on the table had not been in Nicklaus' hip pocket.

In fact, Aoki might not have made those birds had he known that by shooting 274 -- breaking the Open record of 275 held jointly by Nicklaus (1967) and Lee Trevino (1968) -- he would get a $50,000 prize from a gold magazine.

Aoki needed three explanations before he understood that his take-home pay for this week would be $29,500 for second place, plus the $50,000 bonus also awarded Nicklaus. "Ohhhhh," said the merry Mr. Aoki, in English, bugging his eyes in a double take, "thank you very much."

That final 72nd hole was a triumphal march for Nicklaus, similar to his walk up the last fairway at St. Andrews in July 1978 when he won his only other major since 1975.

The crowd's surge was so wild, with shouts of "Jack is back," and "Take it on home, Jack" and the like, that few in the crowd of 27,029 noticed that Aoki's 60-yard wedge into the last green burned the edge of the cup for what would have been an eagle -- thereby making Nicklaus' last 10-foot birdie putt a necessity to avoid a tie, rather than a mere touch of dramatic window dressing.

"You can believe I saw it," said Nicklaus.

That final mob scene, alien to golf, but totally indigenous to American sports fans when they are moved by a seminal event in a great hero's career, was properly emotional and on the edge of control.

"Isao and I were just trying to get off the last green with our lives," Nicklaus offered with a smile. Then he added, "I'd never complain about that. These were the most vocal galleries I've ever heard and the warmest reception I've ever gotten anywhere."

Jack Nicklaus, who has won all his Opens on Father's Day and who now joins premodern Willie Anderson, Bobby Jones and Ben Hogan as the only four-time winners, understated it nicely.

"I think that a lot of nongolfers enjoyed what happened today."