Mort Sahl, who once divided Americans into two kinds of people - those he appalled and those he amused - doesn't really smile.

That smile you thought you saw on the Ed Sullivan show, back when Mort Sahl would come out with his sweater, and the rolled-up newspaper, to make cracks about Eisenhower . . . you can see it's just something that happens when he looks at you hard and stretches out that thin upper lip and then all the teeth are shining across the table in the twilight of an Italian restaurant. And he doesn't laugh then, either - it's a noise like somebody slapping books shut: HAHA!

He goes back to his veal piccata. Then he puts his fork down again. He has just been asked what he's interested in talking about on his radio show, which began yesterday on WRCAM.

Among other things are "capitalism and heterosexuality," Sahl snaps. "But you gotta fight for the right to talk about them these days. Capitalism has withstood Marx, but not Ralph Nader." he says, returning to the veal. as if the point is obvious. For one thing, you're surprised to hear him use the tag-words of the right wing with the facility that he used to have with the jargon of the left.

Clarification is requested.

Sahl frowns a tired, puzzled frown. So does his wife, China Lee, who's been with him since her great success in 1964, as Playboy's August Playmate.

Well, the Nader line was a joke, one suspects.

'When kids get out of college, they've been listening to Ralph Nader for so long they think that businessmen are buzzards," Sahl says. And, on heterosexuality: "The women's movement is rather vocal - in fact, strident. HAHA! There's a total war on masculinity. Men say: I'm proud to say I'm ashamed to be a man.'"

China, in shiny brown blouse, leans across the table to announce: "I'm ashamed to be a woman! A lot of women, you know, would like to stay home, but they don't feel like they have the right anymore. I can't tell you how many women come up to me and say: 'I don't want a woman boss.'"

It's suggested that Mort Sahl has moved to the right of his image in his late-50s heyday, back when his audience at San Francisco's Hungry I seemed to be a collection of ex-Trotskyite Zen Buddhist sports-car-driving jazz fans for Adlai Stvenson. "My people," Sahl would call them in his routines.

"Mort's audience is the average working people," say China (rhymes with Sheena).

"I would Vegas for three years, Sahl says. "I played to gentles, average Americans, people who are suspicious of big government, people who listened when I talked about the Warren Commission. Not liberals - the liberals became the perpetuators of the status quo."

"You're not attacking liberals," China reminds him.

"I was born in 1927 in Jefferson's America, Walt Whitman's America, the America of adversary proceedings."

We don't have adversary proceedings?

"There was none for Jack Ruby or Spiro Agnew," Sahl says, with gravid grimness.

You'd rather be laughing.

In 1953, Mort Sahl appeared on the stage of the Hungry I (for intellectual), jettisoning the mother-in-law routines and ethnic jokes (So the rabbi says "Pardon me, father . . .") and all the general booze-and-smut inventory of nightclub spielers.

"Humphrey said that Eisenhower should take a black girl and walk her into a segregated school," he'd say. "But Eisenhower is having a terrible time deciding on how to do it, whether or not to use an overlapping grip."

Print, of course, does no justice to the savage, staccato amazement of his delivery, punctuated by cries of 'where was I?" and "Onward!" as he did his syntactical tap dance across John Foster Dulles, the University of Miami, war movies, advertising men, segregation, psychoanalysis . . .

Like one coffee house routine: "It's 3 a.m. People get up and put on their sandals. They say "I hate to go but I have to get up and go to Europe in the morning."

"Or the U2 bit: (about the noted CIA spy plane): "Maybe the Russians will steal some of our secrets now and then they'll be two years behind. Actually, now we've got a U2 surplus. The other day there were leaflets falling from the sky in downtown L.A. They said 'Your picture has been taken and is available for 25 cents.'"

Exquisite: Sahl could take all the cliches, the inchoate stereotypes of an emerging generation and make his listeners feel like they belonged to it. He was the master of the hip allusion, the keywords that said: "We know better."

His audience was the group founded by GI Bill barbarians who took intellectualism away from academics and the affluent; never, however, without a certain uneasiness for which Sahl was a catharis. This was back when you could say "Bloomsday" and all the English majors would break up; "bell-shaped curve," and you got the sociologists, the laughter being a shout of "us, too!" - an advertisement of knowing better, of being hip.

He was one of them: He'd gone to USC after a tour in the Air Force, then hung around Berkeley, sleeping on a window seat and eating pies cadged from a local eatery.

He was the peer of Lenny Bruce and a prototype for many other humorists, some of whom have proved that the half-life of the American comedian is often stunningly short.

"If things go well," he'd tell crowds here at the Cellar Door, or at Mr. [WORD ILLEGIBLE] in Chicago, or at Basin Street East in New York, "next year we won't have to hold these meetings in secret."

The problem was, he was right.

John Kennedy got elected, and the trappings of intellect became so [WORD ILLEGIBLE] they were ordinary. The wonderful "We-few" feeling that he'd both nurtured and satirized eventually vanished. Mort Sahl had been co-opted by reality.

He explained, repeatedly, that the liberals liked me until they became my target," but what was strange was his surprise. After John Kennedy was shot to death, Sahl committed himself to an ultimately unco-optable group-assassination buffs. For four years, off and on, he teamed up with New Orleans district attorney Jim Garrison, going "from $600,000 or $1 million a year gross income to $13,000," Sahl writes in his autobiography, "Heart land."

"I had to live the past 10 years with the word 'paranoia,'" he writes recalling that he was also "accused of the most awesome crime of all in the eyes of show business - of not being funny and beloved any longer . . . Did I at 35 suddenly lose my stuff?"

Yesterday, at 51, from 4 to 7 p.m. on the radio, Mort Sahl was still raging at the liberals, at "what they tried to do to me along the way," at the CIA, school busing, foes of Jim Garrison or anyone else who doesn't think that the Kennedy assassination was a conspiracy, and "the power nucleus" all of this in vague harmony with the questions of listeners, who kept telling him they had to wait for half an hour to get on the air.

By the end of the show, Sahl and the weatherman were trading huge laughs, forgetting about calls as they brought the happy-talk format to radio. He'd only been cut off once as a station promo blew away one particularly enthusiastic conversation about the "power nucleus."

"Before I say goodnight, I want to tell you something," he concluded, his voice dropping. "I believe that America is at stake."