COMEDY REVIEW : Laughs Never Stop With Leno : Stage: Heir apparent to Johnny Carson shows Humphrey’s crowd what sets him apart as one of the country’s outstanding comedians.

When you think of the funniest comedians in the country, a couple of names come to mind. Jay is one. Leno is another.

And when you think of Leno, you think of family entertainment. A heartland humorist massaging Middle America. Someone who finds soft spots where others just find current events, dulling politics or aging parents.

During his first of two sets at Humphrey’s Thursday night, Leno moved seamlessly through 90 minutes of material and underscored a trait that sets him apart from his contemporaries: He was constantly funny. Most comics have a rough time doing 60 minutes without flat spots. Leno kept his show in gear the whole time.

He started by talking about Dan Quayle standing ready to pitch in during George Bush’s recent hospitalization.

“The Secret Service had Dan Quayle right there at his bedside, standing by, ready to go,” Leno said, then paused for a split second. “OK, as a heart donor, but still, he was there.”

Departing momentarily from politics (to which he repeatedly returned), Leno moved on to a custody battle over seven frozen embryos in New Jersey and what life would be be like for them as kids.

“You know, you have to feel sorry for the frozen embryos themselves. It’s tough enough growing up knowing you’ve been adopted. Imagine knowing you’ve been defrosted.”

Leno is easily the most entertaining comic working today. He is the master of humor that is clean, topical, easy to understand and that hits close to the home and hearth.

A fair portion of his act was devoted to politics, planes and parents, especially his own parents.

Leno moves stunningly easily from story to story. In 25 words or less he slides from talking about plane crashes to eating free samples at the supermarket.

Leno’s act mixes current events with chestnuts he’s been doing for years, but you don’t mind hearing about how his octogenarian parents use the $1,200 VCR he bought them as a night light with a flashing 12.

He makes doing comedy look easy, with no trace of the years he has spent honing his act, an act Johnny Carson once panned, saying Leno had only five jokes in his 60 minutes. (The Andover, Mass., native took Carson’s criticism to heart, made some changes and made the “Tonight Show” eight months later. He is now Carson’s heir apparent and subs for him Tuesday nights.)

Leno--looking a little less sartorial in blue jeans and a charcoal sports coat than he does on “The Tonight Show”--is an entertainer who does his homework and takes a fair portion of his material from news reports, like when he talked about the plane that crashed in John McEnroe’s back yard a few years ago.

“It’s true,” he says, again taking the perfect pause. “Well, McEnroe says it was in the yard, officials say it was on the line.”

And, while talking about airlines, he maintains that some of them go too far. Like the one that wanted him to join the “Frequent Survivors Club.”

Or the carrier that has a Flight 5050. “I wouldn’t get on a flight that was 99 out of a hundred.”

He rarely does impersonations, dialects or uses special effects. The act is all timing and material.

Leno shuns histrionics. Thursday night, he simply moved around the stage and relied on inflection and timing to carry his message.

He did it without shrieks or obscenities. He did it without anatomy jokes, minority jokes, sexual jokes. Take those cornerstones away from most comics on the circuit today, and you gut their act.

The closest Leno came to an ethnic joke was when he referred to Chef Henri in one of his jokes as a “little fat French chef.”

The closest Leno came to ranting or getting excited was in the fast-food section of the show. Ironically, it was the only time he drew applause.

“By 1995, all McDonald’s will be connected by a walkway. . . . “What’s next? . . . McHoof, McGristle, McMarrow? This cow’s mother couldn’t identify him with dental records by the time they’re done.”

Leno is also a master of mock incredulity, and no one uses gentle sarcasm better than he does; telling of an article about how most airplane injuries occur on the ground, he looked astounded by the revelation. “Of course,” he said. “It’s not until you hit the ground that you experience that minor discomfort.”

Leno’s act doesn’t suffer when he plays off the crowd, either. He wades into his fans easily and painlessly, proving that barbs don’t have to be stinging or sarcastic to get laughs.

When one San Diego State student admitted to studying political science and Third World countries, Leno said, “Might I suggest a minor in automatic transmission repair?”

For another in manufacturing and engineering, Leno swiftly came back with: “Speak Korean, do you?”

About the only downside to the evening was the wet, windy weather. At times, the breeze through the microphone made that irritating whooshing sound. The 6:30 p.m. full-house performance began with a drizzle, warmed slightly but turned chilly and blustery.

The humor, however, was anything but foul.