There were 3,700 of them, mostly in shirt-sleeves, waiting expectantly yesterday behind the cigar smoke and the bunting in the Los Angeles Convention Center. The United Steel-workers of America were in readiness and the announcement came, finally, that Senator Muskie was ready to address them. "I mean the secretary of state," a convention official corrected himself, and on cue, Edmund S. Muskie raised his right hand to wave at the crowd.

It could have been one of the hundred s of convention halls the former senator from Maine has addressed during his 35 years in politics. But it was one of the first Muskie has addressed as secretary of state -- and quite possibly one of the last he'll address as a man some people think might become president.

Ed Muskie says it never occurred to him when he launched his new career as secretary of state three months ago that "this other thing would emerge out of it all."

Stretched out in the Air Force plane speeding him and his entourage to Los Angeles for a round of election-year foreign policy speeches, Muskie seems bemused by the boomlet of "Muskie for President" talk and the committee that has been canvassing the delegates to next week's Democratic Convention in hopes of making Muskie an alternate choice.

"God knows," he says in that New England rasp, "instead of putting myself on ice, I put myself on a hot spot."

It may be hot, may be "uncomfortable," as he insists, but it's also a little exhilarating for a guy who, eight years ago, looked like he had a good shot at the presidency before the bubble burst and he joined the lengthening ranks of also-rans.

For 65-minutes on plane, he had sparred with the State Department correspondents accompanying him, never convincingly taking himself out of contention though all the while mouthing the words that would seem to do so: "I'm supporting the president . . . I have no political ambitions -- absolutely none . . . I was persuaded by the president that I might have a constructive role to play [at State] and I accept that."

But Muskie, at 66, is a politician not without a sense of gamesmanship or fun. So here, in the forward cabin of his Air Force jet -- which he is sharing with his former Senate colleague, California's Alan Cranston, and freed American hostage Richard Queen -- Muskie is obviously relishing the moment.

"It did surprise me," he says of his renewed celebrity as a possible solution to the mounting democratic disatisfaction with both Jimmy Carter and Ted Kennedy.

"I thought people had forgotten about me by now. I've been buried in the budget process for six years [as Senate Budget Committee chairman], and I didn't think the citizenry was paying that much attention."

After his '72 campaign, he says, he felt that he left people "with sort of a negative attitude about me -- I felt I'd let them down. And I was disappointed in myself." On reflection, he says that if he had it over again he would never have gone down to challenge publisher William Loeb of The Manchester (N.H.) Union Leader. That was a "tactical error" in reacting to Loeb's attacks him and his wife Jane.

At the time, it was reported that he broke down and cried, but he claims Loeb's editorials made him "madder than hell" and choked him up. He says he never cried. More important, he says it was "bad judgment and contrary to a rule I had laid down for myself in public life 25 years before: You

Muskie says he sees no scenario in 1980 that could result in a stronger campaign than one Jimmy Carter could wage for the presidency.

I just don't see any more promising prospect in the party than to support Jimmy Carter, and he has earned the support. So I don't want to encourage anything through the slightest nuance, innuendo, tone of my voice, or in any way diminish his prospects . . . I refuse to concede that I am being swept along." Then Muskie's Lincolnesque features shift into his familiar lopsided grin. "It's nice to be wanted," he says, and gratifying to know that there are people who see him as a presidential candidate. But "it would have been more gratifying eight years ago."

An hour after his impromptu press conference, as the plane is coming in for a landing in Los Angeles, Muskie reappears in the main cabin where the reporters are packing up their gear. He leans his long torso over a seat and announces, grinning: "I'm going to deny everything you're going to write."

At Los Angeles International Airport a short while later, it is Alan Cranston rather than Muski who gets out of the limousine to talk to reporters. A candidate himself for reelection, Cranston is quote as saying Muskie "certainly would have a chance" and would make " a fine choice" as an alternate candidate. But there is a subtlety of survival politics, too, when Cranston affirm that the administration is not counting on him to campaign in California for the president. So it is Muskie and others from Jimmy Carter's cabinet sent here to wage that battle. Muskie will do it, he says, by attempting to change public perceptions of Carter's foreign policy.

Muskie says he is the first political secretary of state since Jimmy Byrnes. To say he was astonished when Jimmy Carter tapped him for the job understates his reaction, Muskie claims.

"It never occured to me to have any ambitions as secretary of state or that I might even be qualified for the job; I never thought about it."

Certainly, in the view of some observers, what Muskie lacks in foreign policy expertise he makes up for in enthusiasm. Inclined to speechify in the fine old tradition of Senate orators, Muskie does not hesitate to try out lofty views and rhetoric.He is seen by some as non-innovative, by others as a resourceful advocate for Carter's foreign policy and by himself as realistic enough "not to raise my expectations too high."

Obviously, he goes on, he knows the period from May 8 (when he took office) to the end of the year is a political year promising a "tough struggle" on such questions as the Middle East, Afghanistan, Iran and arms control.

He feels that his long experience in politics is a definite political advantage in his new position: "My impression is that it makes a difference to my colleagues in foreign ministries around the world -- they are all politicians from parliamentary governments. They perceive that I have a relationship of my own and so when I give them on congressional impressions and cite obstacles, my statements make an impression on them."

Muskie does not pretend to be an intimate of Jimmy Carter's, but there is a statehouse camaraderie that develops among former governors like them. Four years ago Carter considered Muskie as a running mate Muskie thinks he turned to Mondale instead because of advice the Maine senator gave then-candidate Carter.

"When he first came to Washington after the primaries and said he wanted to talk about vice presidential candidates. I said first of all pick someone of your generation," Muskie recalls, "Second, pick somebody who's gone through the primaries and and third pick someone who's acceptable to a wide segment of the party. I think the first reason was the reason."

Whatever the reason -- and there are some who do not discount Muskie's sometimes volatile temperament -- Jimmy Carter felt no hesitation in turning to Muskie this spring as Cyrus Vance left the administration in a protest over handling of the ill-fated rescue attempt in Iran. The invitation to Muskie came at a time when he was thinking seriously about not seeking reelection to the Senate in 1982.

"The Senate is really rather confining," says Muskie, adding that "I wanted to be liberated a little bit. So when this came along, totally unexpected, it seemed like a great way to cap it all off, to get a new experience, maybe for eight months -- maybe for four years and eight months. I was excited about it."

It is a whole different world down there in Foggy Bottom from what it was on Capitol Hill. For one thing, say reporters who cover Muskie, every time he opens his mouth nowadays people listen. On the Hill, what with the Ted Kennedys and the Bobby Byrds monopolizing athe microphone, this was not always so easy.

Muskie's new stature became starkly evident to some when he accompanied President Carter to Venice in June. When the Soviets announced they were pulling some troops out of Afghanistan, Muskie was the only high official around to comment on it, And when a reporter leaned over to ask what he thought of the development, he replied something to the effect of, "Don't believe it till you see it." The quote topped some news stories, surprising even Muskie.

Besides his new-found quotability, Muskie finds other trappings of office equally pleasurable, according to some reports. There are the omnipresent State Department bodyguards running interference wherever he goes, and the elaborate and even elegant domain atop the concrete and glass State Department headquarters with the second best view in town. There is the hustle and bustle of a cast of thousands and the heady realization that foreign policy-making, in Muskie's own words, "is the supreme political act because it affects not only the lives of people in this country but of people all over this planet."

Says one reporter with some amusement: "He's like a kid on Christmas morning with all his perks."

When Ed Muskie became secretary of state, his wife told him not to expect her "to walk two steps behind or carry your train, because I won't do it."

That's Jane Muskie, 53, in a nutshell. Friends call her "self-possessed, friendly, unassuming." There's no nonsense, no pretense" about her, friends say.

Her candor is, at times, troublesome for her. In 1972, she thought she was being forthright in discussions with reporters on a campaign bus trip across New Hampshire. The story thatultimately contributed to her husband's downfall, characterizing her as a gum-chewing, joke-telling, indiscreet political wife, still rankles her. "It was kind of dirty pool," she says. But she doesn't dwell on that part of the past. She was sorry that Muskie never went all the way -- "i suppose hope springs eternal" -- but she felt much worse in 1968, when her husband was vice presidential running mate to Hubert Humphrey.

"Oh, what we would have spared ourselves if those two had been elected," she says of their defeat by Richard Nixon and Spiro Agnew.

The present presidential murmurings do not seem to excite her. "It has happened so many times," she says, but she doesn't think anything will come of it.

One consideration that went into Muskie's leaving the Senate for the cabinet was financial, since he had to take a salary cut of $9,000 as well as give up about $25,000 a year in honoraria from speeches. With two children in college, she says, it was no small consideration.

With all four Muskie children grown and away this fall, Jane Muskie will devote some of her time to a book project with another former Senate wife, author Abigail McCarthy. Muskie's task is the research.

In at least one instance, a hospital scene in the book, she has had plenty of experience of late: this week, the Muskes' eldest daughter Ellen, 29 underwent back surgery. Earlier this spring Jane Muskie herself had gall bladder surgery. And a couple of years ago her husband had surgery related to a broken back he sustained years ago when a railing collapsed and he fell down a stairwell. (A morning ritual that the secretary follows, wherever, he is in the world, is an hour of exercises for his back, according to his wife.)

Despite her husband's contention that he probably wouldn't seek relection in 1982, Jane Muskie says, "Ultimately, I think he would have run again. It's the nature of the beast. there's no good way out. and he is truly a public servant." she said he misses the Senate, but that was a little tired of the same problems and that taking his present post was "a graceful way out."

"It was just plain hard work for him. He went from Mr. Clean to Mr. Mean. And I think a lot of the temper thing stemmed from that," she says.

When Muskie started out in politics, she says, "it was a very respectable ambition, but nowadays, it rates less than garbage collectors." After 23 years in Washington political life she says you learn how to operate. "Washington is such a unique place that it's beneficial for an office-holder to know the scene very well. Washington is a big small town, and doesn't easily open up. You know they always say that the Senate is the most exclusive club in the world, and I think," Jane Muskie continues, "that the senators really beleive it."

The future now might seem considerably more uncertain to the political poll-watchers who are clocking Jimmy Carter's popularity. But Jane Muskie claims she has no qualms about that, because all sorts of interesting things can happen. "Ed is a very good writer, and speaker. We've realy led charmed lives."

But as for politics, says Jane Muskie, "there's no place for him to go, he's had everything."