A bridge player thinking seriously of bidding a grand slam is facing one of the biggest, baddest decisions in the game. So it was no surprise to see Marc Franklin writhing in his chair like a kid whose pants don't fit.

Stroke went Franklin's hand on Franklin's chin. Flutter went his eyes. Nervously, he fanned and unfanned his cards. Finally after about 30 seconds, he just shrugged.

"Seven no trump," he said.

"Pass," said each of the other three players in turn. Two of the three uttered the word casually, almost diffidently. But the middle passer was a guy named Levey, and my bid was seasoned with dread.

This was the second hand I had ever played as the partner of Marc Franklin, King of Bridge. I truly did not want it to be my last. Kings of anything don't like declaring that they'er going to take all 13 tricks and ending up with one or two less. Nor do kings -- or newspaper types -- like the backbiting and homicide that can follow.

But as soon as the opening lead was made and I had put down my dummy, Franklin began smiling. As soon as each opponent followed to two arounds of hearts (see diagram below), Franklin could count 13 tricks. South deals.

As he was notching up our 2220 points, for a vulnerable grand slam in no trump, bid and made, Franklin looked across the table. He waited for his less-than-royal partner o quit sighing with relief. Then he said: "Nicely bid."

With such results and rapport, it's no wonder that Franklin and Friend went on to capture eight place in a field of 88 in the open pairs of a sectional tournament in Baltimore two Saturdays ago. The Tournament was run by the American Contract Bridge League (ACBL).

The day provided each of us with shelter from the rain, 1.73 master points -- and an anguished breastbeating session on the way back to Washington as we rehashed the three mistakes (all mine, natch) that kept us from winning.

But the day also provided the investigative reporter's dream. Evidence. The goods on 20-year-old Marc Franklin, King of Bridge.

The kid can play, folks.

Throughout eight hours and 52 hands, under the intense scrutiny of a columnist/partner who happens to be a life master and who occasionally plays like it, Marc Franklin did not make a single error.

None. Not in the bidding. Not in the play. And not, it is a pleasure to report in terms of decorum, either. If Franklin isn't the King of Bridge Politeness he is at least the Prince.

But Franklin's title and notoriety in tournament bridge circles have nothing to do with pleases and thank yous. The ACBL named him King of Bridge in 1977 because, when he graduated from high school in Palo Alto, Calif., that spring, he had amassed more master points (315 at that time) than any other high school student in America.

That feat won Franklin a four-year scholarship to Claremont College in Pomona, Calif. And Franklin's excellence as an economics and mathematics student there won him an internship here this summer with the General Services Administration.

The summer has been "great so far," said Franklin. Not only has he managed not to get indicted for corruption, but Franklin is working in "econometric modeling" at GSA, the computer subspecialty he hopes to study in business school.

Meanwhile, most evenings and weekends, Franklin is cutting a bit of a swath through the Washington bridge world. He is now past 600 master points and climbing.

The second diagram shows how.

East West vulnerable. North deals.

Opposite a partner who had shown a very weak hand, Franklin had a delicate bidding decision when East's three hearts rolled around to him. It's the kind of dilemma every serious "bridgie" has lost sleep over -- and it's the kind that sends those who finish in the money to one side, those who end up in the mud to the other.

Franklin could have bid four diamonds (a popular choice, but down one, for minus 50 points). He could have passed quietly (for plus 100 points, and an average result). But he opted for a very close double. He scored two trumps, two diamonds and a spade -- just enough to smell like a plus-200-point rose.

Marc Franklin learned such tactics at the knees of his father (a lawyer and mother (a college professor), both of whom are life masters, too. But his favorite and most frequent partner is his 18-year-old brother, Matt, who was King of Bridge in 1978.

The Franklin brothers first won a "rep" in the bridge world when they captured a masters' pairs in a New Year's weekend tournament nearly three years ago in Reno, Nev.

But youth had to wait to be served. When the scoresheet was posted showing that the Franklins had won, they dashed to a nearby casino to tell their crapshooting parents -- only to be barred by a guard because they were under age.

Marc Franklin "never thought I'd be King of Bridge, and it wasn't particularly a goal." Nor does he feel changed as either a person or a player because of it. If anything about his title troubles Franklin, it is all the hours he has spent "guessing queens" when he could have been doing something else. "The old argument about getting out and doing other things when you'er young -- there's a lot to it," Franklin. said.

But:

"There's a lot of ego gratification in bridge. It's one game where you can sit down against older people and win. Besides, when people have heard of you, when they know you'er a good player, they just go to pieces."

Whereupon, an elderly lady sat down to play against Franklin. he greeted her with a sweet hello, as he unfailingly does. She did a double-take when she recognized him. "I didn't realize I was in the presence of roy-y-yalty," the lady said.

Marc Franklin just smiled. And when she blew a trick on the first hand, he smiled a little wider. CAPTION:

Picture, Marc Franklin, By Craig Herndon -- The Washington Post; Illustrations l and 2, Bridge hand.