The white jet roars past -- "United States of America" emblazoned in huge blue letters on its side. Whipping up wind, it touches down as waiting Democratic politicians -- some giggling like schoolkids waiting for the teacher -- scurry into place in a receiving line.

Out steps First Surrogate Rosalynn Carter, ready for another day of handshaking, smiling and proselytizing on the campaign trail.

Meanwhle, back at the White House, the First Caretaker of the Rose Garden beckons to Pennsylvania television and newspaper people who have suddenly become more important than Scotty Reston or Rupert Murdoch or John Chancellor or David Brinkley. They come running. Part of the presidential schedule these days is to chat it up with media from states that just happen to have a primary looming over the hill.

This time Carter drops the nugget that Khomeini will not release the hostages until after the November election. It will be the biggest of news in Pennsylvania, as everyone speculates that Carter might be preparing the public for military action. Carter's comments coincided roughly with a recent poll that shows 55 percent of Americans favor force in Iran. And once again, Carter introduces yet another bulletin on the fate of the hostages on the eve of yet another primary.

On the domestic scene, Carter blasts Ted Kennedy as the "largest spender" in Senate history and makes him out to be a spoiled churl who might force a Democratic convention showdown with a rules fight.

Yes, for Carter, as well as his wife, it was just another day on the campaign trail. 50 Surrogate Days

The Carter campaign is slick, well-oiled, professional, as the president's cool technicians map out primary blitz after primary blitz. At the height of the primaries, they were right on target with their fall projection: 400 paid staffers and a well organized campaign in 31 states. Right now the campaign is raining money and surrogates and goodies in the shape of grants and favors of Pennsylvania.

They are spending $800,000 here, a whopping half of it on media -- twice what the struggling Kennedy campaign can afford. More than two dozen Carter surrogates -- from Vice President Walter Mondale to chief cajoler Bob Strauss, chairman of the committee to re-elect the president, to Aunt Cissy -- bump into each other crisscrossing the state. They are logged with precision. "The decision was to get campaign spokespersons in each of the eight media markets every day," explains Les Francis, a top Carter campaign aide. Their appearances are even labeled "Surrogate Days." Says Francis, "In a 2 1/2-week period we had 50 surrogate days." Traveling over the same turf is Ted Kennedy, the underdog who seems to be everywhere at once closing the gap in this neck-and-neck race, punching away in steel town after steel town on the economy as the country slides into a recession.

Both sides are desperately courting the huge undecided vote as many Deomcrats grumble helplessly that neither Carter nor Kennedy is much of a bargain. Pomp and Perks

Presidents have long used the advantages of the incumbencey -- the pomp of the office, the ability to dominate the news, the federal handouts, the large staff. And President Carter -- although he travels no further from the White House than his telephone or TV set -- has refined the powers of the incumbency to an awesome art that has Kennedy and his aides howling. "It's a slap at the people of Pennsylvania that Mr. Carter is willing to make these inaccurate charges from the sanctuary of the Rose Garden on the eve of the primary," fumes Kennedy, who also says the president was "quite hypocritical" to hit him as a big spender when, Kennedy claims, Carter's own policies have led to high deficits and interest rates and inflation.

In Pennsylvania as elsewhere, Republicans and Democrats alike have stepped up their attacks on the Rose Garden strategy. Some of it is pure political captial; some of it is genuine outrage.

Jim Flug, Kennedy's special counsel, accuses Carter of "trying to bludgeon, bribe and threaten people, using federal grants and the powers of a federal office. If it's not illegal, at least it's unethical. After all, we're dealing with people who ran on the principle of not being politicians."

In response, Rex Granum, White House spokesman, says, "Mr. Flug is entitled to his always passionately held opinion -- but as is often the case, he does not know what he is talking about."

It is indisputable that White House perks make it easier on the Carter-Mondale budget -- just as they did four years ago on the committee to reelect President Ford.

In 1976 Bob Strauss, then chairman of the Democratic National Committee filed complaints with the Federal Election Commission alleging the use of the Ford White House and the Republican National Committee for campaign purposes -- but nothing ever came of his actions.

Aides insist that Carter's decision to stay home is only hurting him politically. Still, it can be aruged that Carter has it both ways -- looking presidential in a crisis while still playing activist candidate through the media, ads, surrogate hypes, White House invitations, phone calls and the like.

When Rosalynn zooms around in the government plane, the cost to Carter-Mondale for a two-day trip is around $10,000 -- a fraction of what a similar charter flight would be. "The basic cost is defrayed as a White House expense," says one administration counsel.

In other words, the taxpayer pays the bulk. "But the first lady can't be running to catch any small plane. She needs it [the White House plane] for security reasons."

She travels with a staff of three, and they do not go off the payroll for their trips, which average two days out of the five-day week. The counsel explained that "basically they still spend more than 40 hours a week on official duties. The servicing of the first lady doesn't stop, and they put in endless hours on official duties."

A White House photographer goes along snapping pictures of Rosalynn with dignitaries. The White House photographer does not go off the government payroll because, as the White House explains, he is taking pictures for "historical documentation." If the pictures are sent back as a token of the first lady's esteem, the campaign pays for the expenditure.

And when President Carter has his picture taken in the White House with visting politicos, football players, black ministers or influential businessmen who happen to reside in the primary state, the pictures, often autographed are generally sent out at government expense; the meetings are usually deemed official White House functions.

Flug grumbles that "complaining about this might sound nitpicky, but if they had to pay for that out of their campaign funds it would sure add up."

Gift-wrapped grants and goodies are a definite part of the April showers, as Pennsylvania politicans find themselves handsomely rewarded for fealty. Just as Democratic bosses in other states found it helpful to go along with the federal Santa Claus, most of the leading Pennsylvania politicians have stayed with Carter.

In the recent past Detroit Mayor Coleman Young, a big Carter booster, got $12 million in housing grants and money for 1,600 city jobs with a $600 million transportation grant coming down the road. Grants were bestowed on faithful endorsees in Flordia, New Hampshire and Maine, and before the Wisconsin primary Mayor Henry Maier of Mlwaukee got a sewer grant.

A few weeks ago Rupert Murdoch, publisher of the New York Post, had lunch with the president. That same morning Murdoch met with the U.S. Export-Import Bank chairman to discuss a loan to acquire jets for his Australian airline. Two days later Murdoch's newspaper endorsed Carter. And a week after that Murdoch got his bank loan at an extremely low rate, saving up to $13 million in interst charges. The White House, Murdoch and the Ex-Im Bank have all denied any connection between the meetings, the endorsement and the loan, but the Senate Banking Committee is investigating the bank's decision to grant Murdoch the loan.

In the past few weeks, Pennsylvania has received a good deal of attention from the Carter administration -- both personal and financial.

On April 5 Commerce Secretary Philip M. Klutznick awarded a $2.2 million grant to establish a nonprofit Philadelphia shoe center. Klutznick's trip was considered "official business," so the taxpayers, not Carter-Mondale, paid for that announcement trip.

Pennsylvania officials supporting Carter got ot apportion some of the 275,000 census jobs that were given away this year.

("Patronage sounds like a dirty word," Strauss told NBC-TV recently. "It really isn't. It's part of the American political process. It's part of the functioning of democracy -- as long as it isn't abused.")

At least 20 calls are made daily by Carter to key supporters.

Nothing seems left to chance. When Ethel Wawrzeniak, secretary of the Elizabeth Township Democratic Committee, complained that no one had ever given her anything, she suddenly got an invitation to the White House reception for the Pirates and Steelers.As Strauss moves through the state, he speaks on a radio show, then promises the producer of the show a steak dinner and an interview at the national convention, if she can get his Pittsburgh interview aired on a radio station in Philadelphia, owned by the same company.

The White House has become a revolving door for the card-carrying faithful. "Some 200 black ministers from Pennsylvania were invited to the White House," sighs Mike Ford, Kennedy's Pennsylvania strategits. "I have no idea what crisis called for the need for so much prayer at once," he joke, "but if prayers are good, Pennsylvania prayers must be the best." Surrogates & Saccharine

From morning till night, Rosalynn Carter slogs through the hamlets and steel mills around Pittsburgh and into the ghettos and wards of Pennsylvania, telling everyone that if they stick with her husband for four more years, things will be just fine.

Her soft Southern accent fills with wonder as she says to 1,500 Democrats at a county dinner that one of the main problems in American is that after four years we have the habit of voting presidents out of office and "we have to start all over again. No wonder we haven't solved our long term problems. We need continuity, we need time for programs to work. tWe need Jimmy Carter in the White House for four more years!"

The next day she was selling the same theme, her voice once again filled with wonder in the exact same spots as she used the same exact phrase.

The people of western Pennsylvania -- an ethnic mix of Serbo-Croatians, Russians, Poles, Germans, Italians -- are accommodating, generous and trusting. A strong sense of family, personal loyalty and patriotism permeates their lives and spills over into politics.

Their places of worshp -- the gold, onion-shaped domes of the Orthodox religions, the spires of Cahtolic churches -- nestle into the hills hard by the steel mills. Sunday in the Greek Orthodox church, prayers were said in Greek and, as a matter of routine, not only the archbishop was blessed but also the president of the United States. One Greek entrepreneur, now wealthy but who worked the steel mills at age 14 as did his father and grandfather before him, said, "there is a sense of extreme loyalty out of respect for the office. My mother-in-law wouldn't dream of voting against a president even if it was Nixon and even Carter, who has gotten us into such a mess."

The Carters hope to capitalize on religious and ethnic family spirits; Rosalynn extols "family" at every stop. The first lady always starts out, "I bring you greetings from the president," and stresses family togetherness: "When I left this morning, I talked with the president. . ." or Amy or her own mother or Miss Lillian will be mentioned. Sometimes, as she leaves the White House, she has just played the violin with Amy. Now there is a status report on Amy's dental condition. "Amy just got a new set of braces," says the first lady, confiding to a group of senior citizens that the braces hurt terribly. "Awwww," say the senior citizens in unison. Mrs. Carter then paints yet another picture. There were so many families visiting the other weekend that "we all went to Sunday school and church, and we all took up a whole pew!"

She soothes their anxieties. "Your concerns are never far from the president." To a sea of white-hair and bifocals she assures that there will be "no cuts in Social Security, no cuts in Medicare," which brings loud claps. Then she says that the president is so worried about the hostages that it "never leaves his mind." She knows, because "I have been close to him for three months" and then, in a pointed reminder of togetherness, "as I have been for 33 years. . . ."

At one large Democratic dinner, there was a sudden proliferation of blue and white Kennedy buttons, attesting to some dissatisfaction in the ranks over the economy. But they gave her a polite reception and stood in her honor when she finished. When Kennedy showed up an hour later, his supporters in the room cheered lustily. Although Kennedy himself employs the ceaseless use of his family, there are lots of laughter from those who indicated that they may have over dosed on the saccharine of First Family fidelity.

"I know there's been a lot of talk about surrogates. I tell you I'm opposed to surrogates in the campaign," said Kennedy, "but sometimes it can't be avoided.So I'm glad to fill in for my wife Joan." Will It Play in Philly?

Behind all of the seemingly effortless family chit-chat of Rosalynn Carter, there is a well-briefed sense of what pays. Some voters are turned off by the use of the family, but many others see the Carters as honest, church-going middle Americans with whom they can identify.

Pat Caddell, the White House's pollster, is one of the chief advisers in Carter's inner circle. His polling information often winds up in Gerald Rafshoon's ads, in the briefing papers that tell Rosalynn and other surrogates what to emphasize and de-emphasize, state by state and group by group.

Cynics, sophisticates and critics might think Carter's emphasis that he is doing the best he can in troubled times could be a negative, an admission of ineptitude. But a large number of working-class people respond sympathetically. When Rosalynn Carter says, "inflation is devastating for all of us," they often nod their heads as if sharing in some communal misery that is no one's making.

Asked how she would answer an unemployed auto worker who might question why he should vote for her husband, Mrs. Carter refused to budge from her litany that the worst thing for the poor and elderly and working class is inflation and that has to be stopped. "The auto industry is suffering because it did not change to small cars -- so it's not the government's fault." Her smle fades, and the voice grows chilly when she is asked about Kennedy's charges that the president failed to use the clout of his office to push for labor reform legislation. "He's been in the Senate 17 years. It looks like if it were important to him he could have done something about it," the first lady kisses him off. "We have worked very hard with labor."

Little is left to chance as Carter-campaign intimates huddle on how put the best face on economic hard times. A regular Monday briefing with the president includes Hamilton Jordan, Jody Powell, Gerry Rafshoon, Bob Strauss, Pat Caddell and Tim Krfat and, as Kraft says, "always Rosalynn." Jordan is in daily contact with the Carter-Mondale people.

It has been said that Carter is a better campaigner than a president. It is clear that his staff -- shrewd, tough, professional loyalists from Georgia or the 1976 campaign -- enjoys the battle. There is a touch of cockiness as Kraft sips coffee in his grungy K Street headquarters with tattered carpet and clutter. All campaign headquarters, prosperous or not, have that same aura of tacky impermanence.

Even if they lose the popular vote tomorrow in Pennsylvania, Kraft is certain Carter will gain enough delegates to roll up a victory that will leave Kennedy in the dust.

There was a front-page story the day of this interview stating that Kraft had arranged the White House lunch with Mudoch. All he did, says Krafts, was "relay the request" from Carter's New York campaign manager. "Hell, I do that six times a week. If anyone is not aware of the 600,000 subscribers a day to the Post or Murdoch's media influence you're crazy." It may have just been good politics, but what about the timing of the loan? "I didn't know that till I read it in the paper," said Kraft.

Kraft's pal Rafshoon, down the block on K Street, has spent recent weeks in his posh office with his Andy Warhol silkscreen portrait of Carter masterminding electrnoic media ads that are strongly critical of Kennedy. "We felt the voters were turning against Carter -- an forgetting why they don't like Kennedy," said Rafshoon with a grin. "We're just reminding them."

Voices of people on the street in Wilkes Barre, Scranton, Pittsburgh and elsewhere run together in these ads: "I trust Carter more than Kennedy . . ." "He's too liberal." "I don't think Kennedy can deal with the crisis . . ." Rafshoon looks innocent and laughs as he explains that "we just went out and found people on the street. This is what people say." Asked if he thought Kennedy would give up after Carter won the nomination, Rafshoon laughed and said, "Yeah, I don't think he's that much of a spoiled brat."

One TV ad emphasizes Carter's famly life, saying, "I don't think there's any way you can separate the responsibilities of a husband, father and basic human being from that of being a president." Carter is sitting at the White House with Amy and Roaslyn. A voice-over says, "Husband, father, president. He's done these three things with distinction." The suggested comparison with Kennedy is raw and obvious.

Rafshoon also says that "since the president isn't campaigning" they have not filmed him on the stump. However, taping his voice is another matter. At the end of one Pennsylvania radio ad saying that the president is a friend of the steelworkers comes the unmistakable Southern voice: "This is President Carter, and I'm asking for your vote in the Pennsylvania Democratic primary. . . ." Pressing the Flesh

Rosalynn Carter is in McKeepsport, a steel town southeast of Pittsburgh.

Crowds jam a shopping mall, drawn by the magnet of the motorcade, the TV cameras, a chance to see the first lady.

Unlike New Yorkers who felt angrily spurned by Carter's not coming to visit, the people of Western Pennsylvania seem more tolerant and feel honored that the first lady comes instead. There are some dissenters among the macho steel workers who say "I don't like it -- she wears the pants in the family." But many more are like Geraldine Gibala who tends bar in a restaurant and tavern and says a lot of her customers are for Carter. "I don't mind him not coming. I guess he's busy, you know? I understand that. It's nice she could be here."

People crowd forward for a glimpse of her, and then suddenly the crowd goes mad. A tall, dark man with dark sunglasses approaces. There is true, genuine excitement now. "Franco Harris!" they roar. In this sports mad world, the Pittsburgh Steelers star is king. The Secret Servicemen, who cannot leave their posts, whisper to staff aides to get his autograph for their children.

Rosalynn, swept up in the wave of humanity around Franco Harris, who is supporting her husband, never misses a beat. As the crowd, swirls around them, lured by the hope of shaking hands with both the first lady and Franco Harris, she reaches out for those that can't get to the football star. He takes one side of the street, and she takes the other. Presses the flesh, knowing that will mean a special greeting, that people can tell their friends, "I shook hands with the first lady." She leans forward as if sending an intimate message to each one.

"Vote for my husband. I hope you vote for my husband on Tuesday."