Ronald Reagan may be the Teflon President, but don't say it doesn't rub off. Now there's the Teflon Son.

You do know him. Just turn on the tube and there he is, Ron Reagan, newest of those American Express card unknowns doing his part to eliminate anonymity for an undisclosed sum rumored to be in six figures.

He's the 101st Do-You-Know-Me? in the 12-year-old series, and as he puts it in the 30-second commercial you'll be seeing a lot the next two years:

"Every time I appear on a talk show, people ask me about my father. Every time I give out an interview, people ask me about my father. Every time I pull out the American Express card, people treat me like my father. Pause. Come to think of it, that's not so bad!"

A card with Ron Reagan's name flashes across the screen. He's standing in an airport phone booth saying, "The American Express card, don't leave home without it!" And then, into the phone, he says, "Hello, Dad?" and "excuse me" and closes the door to carry on his conversation with the other Ron Reagan, who is, of course, the president of the United States.

The response to Ron's pitch? A modicum of clucking over luncheon tables, and some not-for-attribution sniping about his going strictly-for-the-buck. But mostly people just say, "Oh, isn't he adorable?"

How does he get away with it? To some Washington insiders, it looks like a classic case of "like father like son": Nothing bad sticks.

Even brother Michael Reagan, who himself was criticized for trading on the Reagan name early in the administration, is forgiving.

"Sure," he says. He laughs. "If someone wants to pay me, I've written my own:

" 'When I go to dinner, they think I'm my brother. When I go to the ballet, they treat me like my brother. If it wasn't for American Express, nobody would know whose brother I am.' "

He chuckles. His version would clearly distance him from any commercialization of the president because "I'm not using my dad, I'm using my brother," he says.

*A spokeswoman for American Express says the White House asked for a copy after Ron's commercial started airing, but that no one there saw it or the script ahead of time. For the record, the White House has not objected to the commercial.

"It doesn't feature the name or likeness of the president or first lady. It features the name of the president's son," says Christopher Cox, who, as senior associate counsel to the president, has seen it.

*Ronald Prescott Reagan, who is 28 and not to be confused with Ronald Wilson Reagan (although come to think of it, that's not so bad), is no longer a second-rate ballet dancer. He's a multipurpose writer, entertainer and now salesman who seems to have found his way to fame and fortune.

The American Express commercial is just the latest in the list of credits to Ron's starring role as the Teflon Son.

As a ballet dancer turned television entertainer, he danced before a nationwide "Saturday Night Live" audience in his underwear.

As a photographer's model he cavorted in briefs, the results of which appear in the July issue of Vanity Fair magazine.

As a magazine journalist he writes for Playboy, traditional target of bluenoses as well as the new pornography commission of his father's own Justice Department.

Through it all, he is unabashed and makes no apologies; during his "Saturday Night Live" appearance he even acknowledged in a joke that his connection to his father was the real reason he got the gig. "I'm the least ambitious person you've ever met," he said in Vanity Fair. "All I want is to be insanely happy."

And except for an outraged blast from TV evangelist Jimmy Swaggart about the "Saturday Night Live" briefs bit -- "It's an abomination!" -- he gets remarkably little criticism.

Michael Carlisle, his New York agent since 1982, makes no apologies either.

"He is not in any way a fan of pornography," Carlisle has said. "He is also not a fan of people who seek to trash the First Amendment."

Thanks to Carlisle, Ron's name and face are increasingly familiar. He interviews other celebrities for ABC-TV's "Good Morning America." He has been signed for a small part in a movie. His byline has ridden atop eyewitness reports from the Geneva summit, the 1984 Democratic and Republican conventions and May Day in Moscow. He has written about his dad on Father's Day for the new Fathers magazine.

But the American Express endorsements -- there also is a 15-second ad -- seemed another step. Ron, out of the country on vacation, according to the White House, is unavailable for comment on whether it all adds up to commercializing President Reagan.

And those who are here to comment? For the record, it doesn't seem to matter which party you call.

"I think he does an excellent ad. He comes across as nice, young and kind of cute," says Joe Canzeri, former White House aide.

"He's a television presence -- has a wonderful voice, a Dick Cavett quality. There's texture to his voice," says Chris Matthews, spokesman for House Speaker Thomas P. (Tip) O'Neill (D-Mass.). "I love the one of him calling up the father. It's humorous. It's the use of some talent."

"I think it's probably up to each viewer to decide what to think," says Carlisle. "Ron has a light touch in his relationship with his father, and the commercial highlights that."

He also has a stage director's touch. Carlisle says it was Ron who thought up the "high point" of the commercial, the "hello, Dad" line and shutting the phone booth door for First Father-First Son privacy.

Michael -- Ron's half-brother, who was adopted in infancy by the president and his first wife, actress Jane Wyman -- also hustles acting, talk show and writing assignments, but with less success.

He was the first of Reagan's children to trade on the name after Reagan moved into the White House. Michael got into hot water when the world learned he wrote letters to military installations on behalf of a potential supplier he represented and mentioned his father's name.

Not that the brothers have had a monopoly on capitalizing the Reagan name. In 1982, Maureen Reagan (Wyman is her mother) was accused of taking advantage of it when she ran an unsuccessful campaign for the Republican nomination for the U.S. Senate from California. President Reagan, claiming that he supports GOP nominees only after primaries, withheld his endorsement.

And earlier this year Patti, who dropped the Reagan name for Davis (her mother's maiden name is Nancy Davis), came under widespread, sometimes vitriolic attack for her roman a clef about a president and his family, whom everybody recognized as a version of the Reagans.

Of half-brother Ron's American Express commercial, Maureen says: "He's a good actor, looks good and got paid. What more can you ask out of life?"

Maureen takes a free-enterprise view of the Reagan name. When she was on radio in California, she says, she was "reading 17 commercials an hour and everybody knew who I was."

Trading on Dad-the-president may not be all that new, whether offspring mean to take advantage of White House name recognition or not. There were all those Roosevelts, in the news for years as politicians and entrepreneurs; Margaret Truman, the concert singer and actress; Julie Nixon Eisenhower, the Saturday Evening Post contributing editor; Lynda Bird Johnson, the Ladies' Home Journal correspondent; Steve Ford, the soap opera actor; and his sister Susan, the photographer.

Presidential brothers haven't been above cashing in, either. J. Vivian Truman, Sam Houston Johnson, Donald and Edward Nixon and Billy Carter were all criticized for capitalizing on their fraternal connections.

Michael Reagan says it's just part of the typecasting that the public does with first families.

"What happened to me at the beginning of Dad's presidency was that we'd just come off the Billy Carter years," he says, "and a lot of people were trying to find out who would be the Billy Carter of the Reagan years.

"You get blamed for using the name whether you use it or not. Frankly, if I were going to use somebody's name, I would use my mother's "Falcon Crest" star Wyman . She makes more in one month than my father makes in a year."

*If Ron doesn't get blamed, White House watchers say, it's because he's seen as a chip off the old block with the same sense of style, humor and aw-shucks personality that keeps criticism from sticking to Ronald Wilson Reagan.

Another plus, say insiders, is that Ronald Prescott Reagan's mother adores him. "Nobody's going to talk about her child," says one. "He's the apple of her eye."

*Carlisle says Ron's a "nice unpretentious personality who happens to be himself first." He gets away with things, like wearing his underwear to do the rock dance on "Saturday Night Live," or wearing an even briefer pair in Vanity Fair, because he was a dancer and is "comfortable with his body," Carlisle says.

*It may not be all that surprising when you consider how the president got his start.

"Ronald Reagan made a screen test in a bathing suit," says Matthews, an astute, if obviously partisan, observer of what does and does not play in Washington.

"This kid does it in Jockey shorts."