Outside the porthole window of the zoo plane, mariachis raucously serenaded a crumpled old Volkswagen parked on the runway apron.

"That shows just how hard up this plane is for news," Gary Schuster said with the bemused look of a man who, as Washington bureau chief for the Detroit News, has been following all this for 16 months with Ronald Reagan. d

The battered bug's loose bumper hung just inches above the runway tarmac, upholstery stuffing oozing out of an open door -- a perfect prop, framed against the gleaming wingtip of Leadership 80, for scores of cameras ringing the incongruous scene.

The zoo plane, whimsically dubbed by its denizens, members of the national media, follows Reagan's LeaderShip campaign plane in an apt merry-go-round fashion.

Rep. Paul N. (Pete) McCloskey Jr., a California Republican who once said Ronald Reagan was qualified only to represent the San Andreas Fault, stood in a Prince Valiant pose in front of his ancient campaign car -- the perfect lure for the hardened press.

Then McCloskey dutifully announced that Reagan was now preferable to President Carter. Cameras whirred and tape recorders spun as 100 members of the national press corps just as dutifully monitored the hoked-up history of 1980.

"Sure, they can manipulate us," said Schuster, who was almost alone now inside Reagan's lead campaign plane with Buzz Ard and Barbara Wa Wa, two fully accredited stuffed animals hanging from the overhead luggage racks with press credentials draped around their necks.

"They know what will happen when they set up something like this. They know it and we know it. But we're all out here justifying our very expensive existence and the next shot at any news at all is two hours away in Seattle."

The most wizened of media manipulators call it feeding the animals, and it is a part of the campaign the public rarely sees. The morsels show up regularly as well-crafted newspaper stories or compact television reports, but the life of those being fed shares little of the neatness of those reports.

To begin with, the animals have a voracious appetite. A single television network can chew up 3 1/2 hours of videotape in one day with Reagan, the product winnowed down to less than two minutes for Uncle Walter's nightly delivery to the nation.

The costs are staggering.The television networks alone budgeted $100 million for the longest presidential campaign in history. One newspaper editor estimated each story off the plane costs a minimum of $1,000, exclusive of salaries, but others think that estimate is far too low.

To make the estimates exclusive of salaries is to drive any accountant bonkers.

Bob Dunn, a Los Angeles-based giant who packs his 30-pound CBS camera the way a lesser man would carry a Nikon, normally ears $575 a week. But with 115-hour weeks, overtime guaranteed by his union, Dunn says he will earn more than $100,000 between January and November of this election year.

Dunn, who first started filming Reagan when the candidate hosted the General Electric Theater a generation ago, figures he earns every nickel. He clings upright to the back of open station wagons in 50-mile-an-hour motor caravans, ready to leap off for the next animal feeding, the always lurking gunshot from a rooftop, or another slip of the candidate's tongue.

To think the animals don't bite back, that they don't batter away at the manipulation, is to think that sheep will lie down with wolves.

Reagan started his 7,000-mile journey last week, glowing in the wake of an innocuous encounter with John B. Anderson.

His earlier bloopers seemed back under control, threatening press conferences were ruled out for another week and the campaign was packaged neatly into stock sketches, crowd-pleading one-liners, special messages for special groups and buckboard rides in the Ozarks for camera crews.

By the second day out, however, big black headlines in Miami were trumpeting the fact that Iraqi jets were bombing Iranian oilfields and the package slowly started to unravel.

Reagan struggled gamely to keep the outside world from invading the comfortable vacuum of LeaderShip 80. Off the plane, however, Reagan was cornered at ever entrance to a Howard Johnson's and every exit from a Marriott with a deluge of questions about the smoldering tinder box in the Middle East.

Reagan's recluctant responses gradually evolved from "no comment" to he didn't know anymore about it than the reporters to war is tragic. Finally, in El Paso 48 hours after the first bombs dropped, his aides put out a brief statement blaming it all on Carter.

Jody Powell, the leader of the president's assault forces, quickly branded the statement an irresponsible intrusion in an explosive situation. Reagan pulled back in his shell and, by the time he reached the West Coast, he was greeted by signs from his supporters imploring, "Don't React."

He also was greeted by a San Francisco Chronicle "Top of the News" column that listed his arrival 12th among the day's events. The listing was 10 notches below an item announcing that the courts would allow a portable toilet owner to keep "Here's Johhny" on his water closets despite the protests of the talk show host.

Life aboard the zoo planes is so other-worldly -- capsules of airborne adversaries beamed down like Star Trekkers to one alien environment after another for months on end -- that almost no one aboard believes he or she is seeing or transmitting more than a narrow slice of campaign reality.

"I'd be absolutely horrified if these planes provided the only campaign coverage," said Bill Plante of CBS News. "We live in a cocoon, talk to the same people all our waking hours and are completely cut off from normal life and outside stimuli."

A typical day for Plante came in mid-week when he started in Springfield, Mo. zeroed in on a late morning speech in Tyler, Tex.; held tough for a deadline-pressing appearance at an El Paso pants manufacturing plant, and raced off to the local CB affiliate. KDBC, to move his report to New York.

He cranked in Reagan's war comments 22 minutes before air time; shook hands with KDBC's weather dog, a cocker spaniel named Tuffy who wears a slicker when he predicts rain, and then raced off for a commercial flight that trailed the zoo into San Francisco three hours late.

The insular nature of all this has many reporters -- and a lot of editors -- at least somewhat worried about being subtly co-opted by the unrelenting exposure to just one side of the presidential campaign.

Some news organizations shuffle correspondents in and out to try to preserve distance. Others place a reporter on the plane for the duration, except for occasional rest breaks, thinking closeness has its rewards.

"The greatest danger is being absorbed into this," said Larry Barrett, who has traveled with Reagan for Time magazine since the first of the year. "You're a prisoner. But, even if you're a critic, you have to stay plugged in. It's delicate. The answer is to follow your heart instead of your head. Your head is going to follow the logistics and that's the worst place to go."

Almost all the reporters are somewhat defensive about this problem. Each quickly retorts that he first started collecting Reagan's "fractured facts," or that he chased him down on the Klan remark or that he traced some erroneous statistic.

The bizarre life, killer hours and deadline stresses invariably lead to an almost sophomoric mix of high jinks and zaniness -- a psychological venting that usually sweeps up from the rear of the plane late in the day.

"It starts back with the camera crews, who are always clowning," Plante observed. "It spreads through the middle rows of reporters and finally overwhelms the senior writers, who have staked out the front seats but have their images to protect."

At about that time a wet towel is likely to fly through the plane, catching a quite famous television image squarely in the face. And Pye Chamberlayne, a radio reporter who has as many voices and personalities as the late Peter Sellers, and sometimes seems to have the same trouble determining which one is the real Pye, starts a mock news report of the day's events.

Chamberlayne's mock report, usually not distinguishable from the super-hype voice that does the regular thing, lets fly:

"I don't think this campaign can reach a much lower level of nastiness, Reagan press secretary Lyn Nofzinger said today, adding that President Carter has not yet recovered from his case of venereal disease."

"And he hasn't denied it yet," intones a voice across the aisle.

"And he hasn't apologized either," Chamberlayne adds in a staccato punchline.

Then, eventually the plane lands. Nine Secret Service agents exit out the back door first, buttoning coats over their revolvers, hooking wires to their ears and running the rear-seat gantlet of Buzz Ard, Barbar Wa Wa and the totally irreverent camera crews.

"One little, two little, three little agents," the chorus begins. "Four little, five little, six little agents. Seven little, eight little, nine little agents . . ."

Steely-eyed countenances, hard eyes that soon will be flitting across dangerous campaign crowds, turn briefly to "Not again?" blushes and then suddenly everyone is storming out of the zoo again.

All those involved seem at least a bit confused about what really comes out of this mix of craziness and deadly serious business costing millions a week and leading to the election of the most powerful man in the world.

The morning after the landing at SanFrancisco, Reagan began a speech by saying he wanted to make it clear where he stood on the most important issue of the day and he was "as delighted as you are that the 49ers are 3-0."

A few minutes later his eye caught a waving sign demanding: "When Will the Candidates Discuss the Real Issues?"

Reagan looked genuinely perplexed and said, "I thought I have been discussing them all along."

Moments later, the same group of sign wavers placed a similar placard in front of the press: "When Will the Media Discuss the Real Issues?"

Plante, who had spent the week in a zoo and shaken hands with a Texas weather dog, mumbled, half-humorously, "I've been wondering that myself."