Golfers grow to full stature slowly, finding their maturity in the painful process of defeat. First, they are called prospects, then contenders; the next-to-last stage is, often, being an accused choker. Finally, emerging from this tempering fire of failure and self-examination, comes a champion.

By this standard, Craig Stadler --who won the Kemper Open at Congressional Country Club yesterday by seven shots before a record crowd of 35,000-40,000--looks bigger and burlier all the time. Soon, this slouching Walrus, who shot a 13-under-par total of 72-67-67-69--275 here, may stand tallest in his world.

As Stadler stalked the Congressional front nine yesterday, turning this tournament to a yawning shambles and leaving Jack Nicklaus limping in his wake, Stadler heard words that reminded him of the past, made his ears burn, and made him vow that he would show his taunters his new place in the game.

"I don't hear many negative things on a golf course, but I heard some today," said Stadler, who has finished second, first and first in the Kemper's three years here. " 'Come on, you can choke. You've done it before.' I must have heard that 30 or 40 times on the sixth, seventh and eighth holes. That got me going. I said a few things under my breath and just got more pumped up."

Stadler is fast approaching the point where those bad old days of foul temper, swing inconsistency and last-round anxiety are far behind. Now, as was the case yesterday, Stadler merely uses his hot emotions for fuel, rather than lighting a match to them and exploding. Now, he dickers with his recalcitrant swing and finds new, improvisational ways to win. Now, instead of visiting the woodland creatures with his Sunday tee shots, he comes out of the box with a blitz of Sunday birdies and puts a tournament to sleep in a hurry.

Not his own rusty swing, not the presence of Nicklaus, not those taunts of the crowd, not even seeing his driver fall to pieces in his hands could keep Stadler from his second consecutive demolition of this tournament.

Stadler began his triumphal round birdie-birdie, built his lead from three shots to six by the seventh hole, then meandered home with a stunningly easy victory that rivaled his six-shot triumph here last year for crunching impact.

Nicklaus (74) faded to a third-place tie with Gil Morgan (73) at 283, one shot behind remote second-place finisher Seve Ballesteros (69). One more shot back in fifth place was George Burns (70), a former University of Maryland golf team captain.

"I wasn't playing that well coming here, but 'boom' it happened just like that," said a beaming Stadler, who had finished 58th and 62nd in his two previous tournaments. "I really don't know what it is, but I hope to hell it doesn't stop . . . I had a fantastic start and coasted from there.

"I'm just happy as a clam."

And well he should be. Stadler, the first three-time PGA winner of '82 following his victories at the Tucson Open and the Masters, pushes his first-place money winnings to $312,058 this season--$83,262 ahead of Tom Watson. He also now is the all-time Kemper Open check casher with $207,052. Heck, Stadler even had a birthday this Wednesday; he's 29 and rising.

This damp afternoon, with two brief showers, Stadler began with an eight-foot birdie at the first hole, then chipped in from 25 feet at the second to shove playing partner Nicklaus five shots behind him.

"When he sees me chip in from the hay, it has to be dispiriting," chuckled Stadler, whose mammoth lead never fell below four shots thereafter.

"I played all right up to the 13th--one under par," said Nicklaus, who was the only player with a plausible chance to challenge. "Then, I drove it in the woods. But, Craig had pretty well won it by then. I made bogey at 13, he made another birdie and that took the wind out of my sails. I kind of limped in."

Nicklaus began by playing the tournament's first 20 holes in even par. He birdied seven of eight holes in midround Friday for a 65, then reverted to form, playing the next 39 holes in even par. His final five listless holes--two over par--simply let Ballesteros, who made a marvelous save of par from the green-side weeds at the 18th, capture the $43,200 for second place.

By the 13th hole yesterday--the same hole where Nicklaus fell out of a tie for the lead with Stadler at nine under par on Saturday when he three-putted from 12 feet--Nicklaus was seven shots behind and knew he was lost.

Finally, by the 18th tee, Stadler could relax and look at one of the most magnificent panoramas in golf. Not the emerald hillsides filled with 35,000 people cheering him, or the tranquil green-side lake, not even the vast Spanish stucco clubhouse framing the final hole.

The sight Stadler adored was that scoreboard. "I could learn to live with seven-shot leads," he said.

That's when Stadler realized once again that Congressional is, for him, an especially lucky place. All week, one club has defined his game--his long and unusually straight driver. Usually, Stadler's major flaw is his occasional snap hook, or push slice with the driver; he's a miserable 111th on the tour in hitting fairways.

So, as Stadler began that final hole--the same hole where a fan stole his golf ball in the trees last year--he took out that trusty driver one final time. However, it felt a bit loose. Stadler tested the head with a soft twist.

And the whole thing fell apart.

"The shaft fell out. Half the head's gone," said Stadler in disbelief. "Thank God I didn't have to use a three-wood on the 18th with a one- or two-shot lead."

This birthday week was charmed for Stadler from the beginning. On Friday, after an opening 72 of which he said, "Probably would have been a 78 two years ago (because of his temper)," Stadler went to the range and began trying to hit left-to-right draws with his irons instead of his normal Nicklaus-like high fades. "It wasn't that I had nothing to lose," said Stadler. "It was more that I was hunting for something to gain."

That brave switch, so typical of the confident, experienced player, probably won Stadler $72,000, as well as an $8,000 piece of Waterford crystal just like the vase he got last year.

As Stadler reached the final green, he pumped his arms over his head, smiled under his mustache and, generally, did everything he could manage to play the crowd-pleaser. Still, it was Nicklaus, of course, who got the mighty cheers. "Show him who he's playin' with, Jack," boomed a voice as Nicklaus attempted a 20-foot birdie putt.

As the putt missed, one fan, presumably a fellow sufferer of Nicklaus', fell into the lake.

What will it take, Stadler was asked, for his fans to live and die with him in that fashion?

"Another 50 wins," said Stadler.

After his performance yesterday, it sounded more like a goal than a joke.