Senator John Glenn; Countdown to a white house bid?

America's third astronaut - the first to orbit - knows that being left behind doesn't mean forever. Waiting your turn, as John Glenn found in NASA and in two unsuccessful Senate races, can leave you sittin' pretty in the long run.

Now John Herschel Glenn Jr. is third again - and waiting again. The polls say he is the leading Democratic alternative to Walter F. Mondale and Edward M. Kennedy for the 1984 Democratic presidential nomination. And Smilin' John is waiting to announce - to run or not to run. The anticipation has everyone else waiting his turn - lined up outside his Senate chamber door.

The press wants to know what it is about someone with a lot of ''formers'' on his resume - decorated fighter pilot, astronaut, president of Royal Crown Cola, International - and now second-term senator from Ohio, that qualifies him for the most powerful office in the world.

Besides getting off-camera practice at squirming imperceptibly in the media hot seat - ''What would you do about Lebanon? The economy? National defense?'' - John Glenn is milking his strategy of productive procrastination for all it's worth. That means keeping the press, the public, his staff, and even his wife interested long enough to figure out if it's worth a shot.

''Well, am I serious about it? Yes, I'm serious about it.'' He is known in Congress for taking his time on major decisions, but he hints he will give an answer by fall. ''We're keeping all options open. That's the reason I've traveled to some 24 states in the last year - and am still doing that. Am I taking this serious? Yes, I am.''

That statement gives you the impression that even John Glenn is talking up the idea out loud until he believes it himself. So does his telling you zealously about the election margin of his 1980 win - the largest in Ohio history, at 1.6 million votes. Leaning forward in his high-backed swivel chair to remind you of his 80 percent recognition factor countrywide or to wax proud of his hard-earned Senate esteem, he seems as if he wants to believe it.

He has the same speckled, Roy Rogers face that graced Life magazine's cover on the eve of his 1962 orbital flight. The yellow hair is tinged with silver, but the grin is still all boy-hero. He will be 64 in 1984, what President-watchers call ''mature without being overripe.'' That is a plus, they say, in a capital that holds youth suspect after Jimmy Carter's ''gang of adolescents.'' And Glenn's genuine-American-hero status, coupled with a certain resemblance to Dwight D. Eisenhower and a low-key style, have led to a nickname, if not yet a formal christening: the ''Democratic Ike.''

Glenn's centrist-pragmatist reputation, anti-Reaganomic rhetoric, and traditional, liberal voting record is considered well positioned for the times: strong advocate of national defense, yet liberal enough on such issues as abortion and the Equal Rights Amendment to be tolerable to most Democrats. And his bedrock, common-sense image reassures those Washington-weary middle-Americans who don't want to wake up with the nation in scandal.

But early-bird campaign-watchers also want to know about John Glenn, the man. Is he smart enough? Is he boring? Can he detonate an audience from the podium? Can he stand in front of a barrage of unanswerables and look articulate? Behind the helpful-senator-from-Ohio smile, is there a big enough sledgehammer?

To give reporters a closer look, Glenn is allowing more and more of them into his inner sanctum. But it's not the catacomb of offices that house his office staff of 47 on the second floor of the Dirksen Building behind the US Capitol.

The inner sanctum is N3864U. His ''Walden'': a twin-engine six-seat Beechcraft Baron. Whenever his wife, Annie, is not along to copilot on one of his 100 trips a year - Yale graduation speech, fund-raiser for New Hampshire Gov. Hugh Gallen, for instance - he sits shoulder to shoulder with a representative of the fourth estate.

The cockpit opens an almost bottomless grab bag of opportunities for favorable comparisons: to his space capsule, Friendship 7, or to the jet fighters in which he flew 90 combat missions over Korea that won him five Distinguished Flying Crosses. But, as one recent trip with this writer showed, Glenn doesn't spend time reliving old glories.

No stories here about shooting down three Soviet MIGs in the last nine days of the Korean war. Not a word about returning safely after being shot up to the tune of 300 bullet holes in the fuselage. ''That happened to everybody,'' he says with aw-shucks modesty when prodded for war stories. ''It wasn't that special.''

As Glenn quietly goes down his flight checklist - engines, fuel, maps, instruments - the observer goes down his for Glenn: steady, self-confident, stable, cautious, diligent. All check. Glenn does not pretend any great measure for genius or charisma here. His style, in the cockpit as in the Senate, is unpretentious, reserved.

Once aloft, Glenn shifts to automatic pilot. He passes the time, hands folded , and contemplates. That reinforces one myth and explodes another. Glenn the distant loner? Perhaps. Wary of trusting his fate to others? Well, he is on automatic pilot.

Nor will he wax nostalgic about the days of the astronauts. Glenn demonstrates his mastery of understatement: ''Compare this trip to Friendship 7, '' he is asked - the space capsule from which he saw four sunsets in five hours. ''Oh, it's completely different,'' he answers. He then leaves the questioner staring at pulsing altimeters, quartz chronometers, and a never-ending stretch of cumulus clouds.

This pleasant, earnest, and Southern-gentlemanly Presbyterian from Concord, Ohio, seems very close to the God, Mom, and Country incarnation portrayed in Tom Wolfe's ''The Right Stuff'' - a 1979 epic on the astronauts.

In that book, Glenn is the God-fearing, good marine who did more than was asked, even prayed in public and kept the boys in line. He was the only one, Wolfe says, whose ''apple-pie image wasn't a lie.'' Wolfe attributes the overnight success of the astronauts in capturing the national imagination to the ''guy with the halo turned on at all times'': John Glenn.

Was the book a fair appraisal?''It's OK, I guess,'' Glenn says. ''He got into the more personal aspects - it was a real competitive group.'' Glenn is not happy with the script for the movie now being made about those years. ''But when your name is in the public domain such as mine,'' he says, ''there is nothing you can do.''

This trip Glenn is to give a speech to the Ohio AFL-CIO state convention in Cleveland, then return immediately to Washington for more interviews at 1 and 3 o'clock. Is his mind on his speech - bringing down interest rates? Is he thinking about his pet project of foreign policy, nuclear nonproliferation? Or how to stop the MX?

''No, not really, there's not a heck of a lot of time to think up here before I gotta think about gettin' back down.'' It's obvious Glenn cherishes the time in his plane, but he says he only uses it for transportation, never recreation. ''Too busy.''

Although he is reticent to talk about the days of ticker-tape parades and roses, a kind of effusive helpfulness shines through. He describes every last dial, knob, and map, willingly giving the rider a crash course in flying. It's all ridiculously simple, he seems to be saying. End impression No. 1: Glenn the stable, unpretentious, grandfatherly type.

Out of the cockpit in a Cleveland downpour, Glenn grabs the only protection available - a plastic, multicolored ''Back the Ohio State Buckeyes'' umbrella - and makes a mad dash for the terminal. A couple of minutes to review the speech, and it's off to a downtown convention center. Jacket back on, hair combed, enter John Glenn, No.2: the fiery orator and powerful senator.

From the podium, Glenn is much more imperial, hard-nosed, and animated. Speaking out against Reaganomic ''voodoo'' policies that he says have brought ''no do'' results, he raises one hand, then the other, then both, even hits the podium. He's learned how to emphasize the key words for bursts of applause.

His speechmaking ability has come a long way since his embarrassment at the 1976 Democratic convention. He has been trying to erase his name from the Democratic Party record books for what many saw as the most excruciatingly boring speech ever given. He preceded the fiery Barbara Jordan and suffered even more by comparison. Usually given as the reason he lost the vice-presidential nod from Jimmy Carter that year, the speech has haunted him ever since.

''Frankly, I'm getting tired of hearing that the President's program hasn't had enough time to take effect,'' he tells a sprawling floor of delegates seated at tables. Glenn's ascension to the podium removes the ''polite'' from ''politics.'' He quotes Budget Director David Stockman as saying that ''unemployment is part of the cure, not the problem.'' He attacks the White House with metaphors of the seven dwarfs: ''If young couples believe the Reagan administration is not responsible for (high interest rates), then they're Dopey.''

When he is backstage after his speech, in a carpeted room draped in red, white, and blue, delegates crush around for photos - and to meet John Glenn No. 3: the People's Choice. A good repertoire of public relations is a must for every politician, and Glenn's uncomplicated, Boy Scout image takes him far in this diverse company. He knows how to project solid personality and strength of character.

Being hustled out the front of the building in time to get back to the capital for appointments, Glenn walks way out of his way to chat and talk seriously with delegates. One expresses concern that his aviation company may be failing. Glenn furrows his brow and turns to his aide: ''Have . . . take a look into this.''

On the flight back, Glenn is more open. He won't talk about past glories but he will talk about humble beginnings.

He discusses the four summers of work at YMCA Camp Nelson Dodd near Danville Ohio, from dishwasher (''by hand - 135 kids, three meals a day, seven days a week,'' he says) to truck driver to counselor. He talks about his childhood sweetheart, now wife of 38 years, Annie, and how she conquered a long battle with stuttering. He tells you about his dad's plumbing shop on Main Street, his schoolteacher mother who was also a church elder.

He speaks of his paper route, election to class president, and marriage to Annie Castor after going through Muskingum College with her. And he runs matter-of-factly through his biography as if it's written right in front of him.

In 1957, Glenn set a transcontinental speed record in an F8U-1 Crusader, flying from Los Angeles to New York in 3 hours and 23 minutes. It was the first cross-country flight to average supersonic speed.

He retired from the Marine Corps in 1965, after serving 23 years and achieving the rank of colonel. With all this history, Glenn is more effusive about his seven years with Royal Crown Cola International.

''I saw more of the world then setting up deals for them than most people will see in a lifetime - all of Europe, Japan, Korea, Hong Kong, Philippines, Lebanon,'' he says.

Those years of learning how to organize people - in advertising, sales, marketing - taught him enough to make it to millionaire status as a real estate baron. The income from two Holiday Inns near Disney World keeps the Glenn empire (plane, homes in Washington and Columbus) well oiled.

Glenn guides his plane into National Airport, flying in close over the Pentagon - ''I can't believe they let us fly so close you can see right in the windows,'' he says. Walking to his 1976 white and gold Buick convertible, Glenn is a regular celebrity. He takes time to tell a cabbie four times that his lights are on. ''Oh, hi, senator,'' the cabbie says, ''I didn't know you were talking to me.''

Out of the plane and back at the Dirksen Building, it's back to John Glenn Nos. 2 and 3: the People's Choice, and hardworking senator from Ohio. The question of what visions he has for America gives him a chance to show his savvy at directing the conversation to his area of greatest concern: education and research.

''The uncertainty about the future that is holding interest rates so high is going to remain until we get these deficits down. You're not going to do that by budget cutting. You're going to do that by getting back into the tax cuts. Now that's short term.'' In quiet, one-on-one communication Glenn speaks in a low tone - but dynamically, smoothly, confidently. His nondefensive, noncombatant style is impressive.

''Long term, what would I do? Long term in the economy of this country, I can't believe anything is more devastating . . . than this administration's cutting of research and cutting of education - higher education. At the very time when other nations are beginning to put more emphasis on higher education and more emphasis on research and just beginning to outcompete us.''

A senior member of the Committee on Foreign Relations, Glenn has made his presence in the Senate felt most in foreign affairs.

Before the Soviet invasion of Afghanistan it looked as if ratification of SALT II would turn on his assessment of whether or not the treaty was verifiable. ''He built up a lot of credibility because he was able to challenge the experts on their turf,'' a Senate aide to Glenn says. ''I think being up there where the ICBMs are going to fly also gave him some credibility.''

He was instrumental in reversing President Carter's proposal to withdraw troops from South Korea. He was a leading figure in seeking compromise on the sale of AWACS jets to Saudi Arabia. And he is the author of the basic US legislation to keep weapons-grade radioactive material out of the hands of nonnuclear powers.

In domestic affairs, he is known as a committee workhorse who can go into staggering detail. He serves on the Special Committee on Aging and the Governmental Affairs Committee. He has worked on a proposal to guarantee access to college loans to teen-agers who engage in community service activities. He favors bailouts and import quotas to aid basic industries as being vital to the national security.

He doesn't always win. He tried to write into tax law, without success, a ''sunset'' provision that would kill off loopholes after a fixed period. And he once horrified his colleagues by proposing a special board be created to hear complaints of job discrimination for Senate employees.

He has also been criticized for taking too long to make up his mind. ''There has been a tendency to procrastinate an idea to death,'' says one of his staff. ''He wouldn't pull the trigger and make a decision. He wanted 100 percent guarantee that nothing would go wrong.''

But after eight years, his reputation and ability appear solid. One White House lobbyist says Glenn is seen as a weather vane of Senate sentiment. ''If we don't have John Glenn on an issue, it will be difficult for us to win, because he is the kind of middle-of-the-road senator whose support we have to have.''

What does the Ohioan have to offer that's different from Kennedy and Mondale?

''I'll let the people judge that,'' Glenn suggests modestly. ''People set up their own criteria (for voting). Part of it's personal, part of it's issues, part of it's party, part of it may be exigencies of the moment. I don't know. (They'll vote for) who's going to provide the best leadership. . . .''

How fast can he move to put together a presidential campaign network?

''I think something like that could come together very rapidly. I don't anticipate that there would be a whole lot of trouble in getting the people and organization and things like that. If I decide to go, it'll be an all-out effort.''

Finally, Glenn has a three-word answer for an inevitable question to any new presidential hopeful. ''The people want to know about John Glenn, the man,'' parries the reporter.

His answer comes with a confident smile and a wink. ''So do I,'' he says.