Late last week, as the House of Representatives convened in frenzy for the battle of the budget, Ronald Reagan's credibility was on the line and Max Friedersdorf was on the case.

The assistant to the president for legislative affairs, after "taking the temperature" of the House for six months and attending the last-minute Republican strategy meetings, had compiled a final "target list" of 50 crucial congressmen. Friedersdorf phoned 30 himself and gave Reagan a list of 20 "fence-sitters" marked for last-minute lobbying. Reagan's "personal contact turned the tide," Friedersdorf says, and when the smoke cleared on the floor the House had passed the largest money bill in the history of the republic by a six-vote margin.

A few days earlier, Friedersdorf had brought the same low-key acumen to bear on the Great Ticket Imbroglio, in which Rep. Thomas Downey (D-N.Y.) suddenly found his ration of White House visitors' passes cut off (a political disaster during the tourist season), reportedly because he had made a disparaging remark about the Reagan family's attitude toward children touring the White House. "I looked into that," says Friedersdorf, "and now he's getting his regular allotment."

Sublime. Ridiculous. They converge on the top floor of the West Wing, where even on a sweltering Saturday Friedersdorf is buttoned up in a three-piece suit and penciling down a thick legal pad of woe -- the collected distresses of his 535 "clients," the U.S. Congress.

It's constant damage control and constant maintenance," says the 51-year-old veteran of the Nixon and Ford administrations. "Congressmen are subjected to the whims, fancies and demands of 555,000 people and those translate into demands on us, which we try to satisfy."

Friedersdorf's position makes him a high-tension conductor in the alternating current of information between the Hill and the White House, the pro in the quid-pro-quo symbiosis of government: The executive branch wants congressional compliance; and the legislators need a bewildering range of services and favors from the executive. He walks across the low-ceilinged room, filled with enough furniture to seat his staff of 11, picks up the sheaf of yellow sheets and reads down the roster of that day's difficulties:

"Call a congressman to tell him that his candidate for a certain position isn't going to make it because of a faulty FBI report. . . A congressman is concerned about a report that an army base in his district may be turned into a permanent illegal alien camp. . . A senator wants the president to come to his state for a fund-raiser . . . another wants to get a boating-accident victim in to see the president."

The welter of worry is "like being in combat," he says. "Unless you've been there, you just can't describe it."

He appears an unlikely field officer, this cordial white-haired man with the front-porch manner and the quiet Corn Belt cadences, a Hoosier in pin stripes, a farm boy who became a journalist because "I like to be near the center of excitement." And now, sitting in one of the armchairs in his sunny, cluttered office, elephant-motif tie snug at the collar and both Gucci loafers firmly on the floor, Max Friedersdorf is only a few yards from the Oval Office. But he scarcely seems to believe it. "How many people from a small town in Indiana grow up and work for the president of the United States? You never grow out of that. You have to keep proving yourself."

Twenty years and eight job changes after arriving here as a Hill aide, he is a quintessential Washington survivor, an old hand at the old-boy network, parlaying past acquaintance into present power. "Access is everything," Friedersdorf says, and he has it. He attends the regular 10 a.m. meetings with the president, along with counselor Edwin Meese, chief of staff James Baker -- to whom Friedersdorf reports -- staff director David Gergen, deputy chief of staff Michael Deaver and deputy press secretary Larry Speakes, "and when [the president] is here and Congress is in session, I'm in and out of there two or three times a day." And he has joined Reagan for the successful series of private meetings with groups of five or six congressmen, a courtship campaign that began last December at Blair House and culminated in last week's budget victory.

Not all the work is so grand. But sometimes securing a vote in an issue as awesome as the budget bill can mean something "absolutely ridiculous," says House Minority Leader Robert Michel (R-Ill.), who recalls Friedersdorf "taking just voluminous notes" during the strategy session and "procedural traumas" before the vote. "Sometimes you don't have to give in on millions and millions of dollars," Michel says, if the member can get one of his constituents "a little two-bit job someplace." And Friedersdorf, Michel says, "can go to Lyn Notziger or a Cabinet member and say, 'Why don't you do so-and-so a favor and just get him off our back.'"

He must be part Disraeli, part maitre d', comprehend the rococo rhythms of Capitol Hill protocol and follow the ever-shifting capacities of congressmen to comply with the president's legislative goals -- when to push, when to let them have a "free ride," when to argue strictly on the merits.For William Timmons, Friedersdorf's predecessor in the Nixon and Ford administrations, the position was "really a desk job," with "incessant meetings" and "a lot of paperwork." But Friedersdorf says, "I think the worst trap you can fall in is to be chained to the White House. If you don't get to the Hill, you lose that touch."

Not surprising, then, that his office looks ignored, with its nearly empty bookcases (a few bound reports and three books: "It's Everybody's Business." "The Limits of Corporate Power" and "Last of the Titans"), ritual photos hung perfunctorily on the walls, the business magazines and Golf Digest squared with the sides of the coffee table. Not surprising, either, that the ruddy-faced Friedersdorf, who likes hiking in the Blue Ridge with his wife Priscilla or playing a little golf with his assistant Powell Moore and former Nixon press secretary Ron Ziegler, complains that he lives "like a mole." Or that he wears a copper bracelet he bought for $1.50 at the Grand Canyon because "I like to have things that remind me of being outside. gI've got shells from Sanibel Island and rocks from the Black Sea."

He tries to get to the Hill every day, stopping in the leadership offices to talk with personal friends like Senate Majority Leader Howard Baker (R-Tenn.) and Michel in the House, continuing his "news-gathering operation" while prowling the hallways.

"He knows the Hill, what makes them tick," says Tom Korologos, Friedersdorf's former colleague in the Nixon and Ford administrations, "and he knows what kind of cigars Tip O'Neill smokes. That's what's important. The big things, like welfare reform, the MX missile, SALT, take care of themselves. What's really important is knowing what door to send the car to when you're picking up a senator."

His day begins at 7:30 a.m., and 50 phone calls and half a dozen meetings later, it ends at some social event around 10 in the evening, although he says, "I don't think you can function much after 7 -- you start getting strung out." He spends 15 hours a week on "night things," especially during the present high season for congressional fund-raisers, where the president's man is a popular draw for potential donors.

Popular, too, on the Hill, where his self-effacing style is a bicameral success. House Speaker Thomas O'Neill calls him "able, tough, decent, knowledgeable and good adviser to the president. He is smart in taking one issue at a time, and not having too many balls in the air at once." Rep. Sam Gibbons (D-Fla.), a ranking Democrat on the House Budget Commitee, says, "He doesn't threaten or cajole, and I'm familiar with those. cI was around here in the LBJ days when everybody twisted arms."

In the fall of 1960, a newly elected Indiana congressman named Richard Roudebush was putting together his first staff. Among the applicants was a 30-year-old Indianapolis newspaperman. "I didn't know him to well," Roudebush recalls, "but over lunch, I was so impressed that I hired him at once."

Roudebush also like Friedersdorf's background. He was a "born Republican," the son of "respectable farming people" of German descent living in Franklin, Ind. He had been born in Grammer, Ind., ("a little railroad stop of about 77 people," Friedersdorf says) and had gone to New Mexico State Teachers' College on a basketball scholarship ("everybody in Indiana is a basketball player or a politician, and some of them try to be both"). It was in New Mexico that an emergency appendectomy got him into his first career: "The head of the journalism department came to my hospital room and said since I couldn't play for the rest of the season, would I mind writing up the basketball games for the school paper. I became a sports writer."

After a year, he returned to graduate from Franklin College in journalism.

"When I was young, I'd change jobs for $2.50 more a week," and he worked for half a dozen papers in Chicago, Louisville and Indianapolis. He had always "wanted to get to Washington on a newspaper," and thought Roudebush's offer "the greatest oppourtunity of my life."

He worked as Roudebush's administrative assistant for 10 years, "more like brothers" than anything else, Roudebust remembers. "He was a very humble guy and a real technician, 100 percent honest and sincere," who "didn't like to see things wasted, whether it was paper clips or typewriter ribbons." Although "never much of a socializer," according to Roudebush, Friedersdorf was weaving a network of friends that would become a safety net for survival. He was active in the Bull Elephnats (a social club for Republican AAs) and the Congressional Secretaries softball game, where he made friends with a freshman congressman named Donald Rumsfeld. And he got to know a number of his House counterparts, including Longworth building neighbor William Timmons, the AA for Bill Brock of Tennessee.

In press releases and newsletters, "Max used to get Roudie in trouble all the time," says Rep. John T. Myers, a veteran Indiana Republican, "because he was more conservative than Roudie was." Roudebush concedes that "occasionally, his conservatism sort of overreached its bounds and made it difficult for me to live up to the printed version of my philosophy." "I came down here as a conservative," Friedersdorf says, "and I've gotten more conservative every day I've been here."

His friend, the late Sen. Hubert Humphrey, another rural Midwesterner, came to the opposite conclusion. "I've thought about that," Friedersdorf says, ever since he accompanied Humphrey to China in 1975 and "he told us about his growing up in Minnesota and how hard he worked. We have identical close backgrounds.I just can't explain that. Maybe Sen. Humphrey's attitude is more generous. He looked at it from the standpoint of helping people, and I looked at it from the standpoint of helping people help themselves. And I don't know who is right, because I think Sen. Humphrey was one of the greatest men of my generation."

During the House years, Friedersdorf went to night school for four years to get an M.A. in communications from American University, and says he still wants to edit a paper some day. But when Roudebush deceded to run for the Senate in 1970, the main chance appeared again in the form of the vacant House seat. He lost in a 12-way district caucus race, came back to Washington disappointed, and went to Rehoboth "and sat on the beach for a week to decide what I wanted to do."

But one old hand washes another: Rumsfeld had been made head of the OEO under Nixon, and offered Friedersdorf the congressional-relations job there. He took it, but less than a year later he was working for another old friend: William Timmons at the White House, who hired him for the first vacancy. Friedersdorf soon became chief liaison for the House (Korologos was his Senate counterpart) and handled the Alaska pipeline legislation in 1973 and the House impeachment effort in 1974, among hundreds of more pedestrian proceedings.

He made the transition to the Ford administration, and became top dog when Timmons and Korologos resigned at the end of 1974 to form a private firm. Korologs says he "couldn't afford" to continue working at the White House salary. But Friedersdorf says he isn't in it for the money: "You only wear one suit a day and eat three meals a day. I just don't think the material things bring that much satisfaction." One thing that does is his family, and he recalls that the social demands of the Ford White House were "very difficult when the children were small. They both turned out great, but I had a lot of guilt feelings." His daughter Kristine, 25, is now at the University of Virginia Law School, and his son Fritz, 20, is studying engineering and architecture at the University of Florida.

When Ford left office in 1977, Sen. John Tower (R-Tex.), calling for "new blood," appointed Friedersdorf staff director of the Senate Republican Policy Committee. He left when President Carter nominated him to the Federal Election Commission. "It was the first job I'd had since college with regular hours," Friedersdorf says, and the first in which he wasn't working directly for someone else. But "I found myself increasingly bored because it wasn't at the center of things," and he readily agreed to become "the president's man" again when Reagan called last year. "When I left here in January of 1977, I said I'd never do this again because it was six years of just incredible turmoil and chaos. But I knew I couldn't live with myself if I didn't get involved in it."

He sums up his migratory employment pattern by shifting to maximum barnyard accent. "When I was in Franklin, there was this old boy that run a clothing store and everybody in town loafed around there. He was kind of a philosopher type, and I went in there one day and said, 'Rusty, what would you do? I've got a chance for to go down to Louisville for $5 more a week.' And he said, 'Why, hell, Max, I wouldn't hesitate. You hang around Franklin and they'll always call you raggedy a -- Max.'"

The budget-bill victory, Friedersdorf says, "will make life much more pleasant for the rest of this Congress," but it was reasonably pleasant from the start. He has profited by comparison with Frank Moore, his counterpart in the Carter administration, who concedes that he did not understand the Congress thoroughly when he took the job. "You can go one of two ways," Moore says. "You can know the president very, very well and get to know the Hill. Or know the Hill very, very well and get to know the president." And he has benefited from Reagan's personal appeal and from the widespread, if arguable, belief that he president has a broad popular mandate. "We all have a high regard for Friedersdof," says Rep. Lee Hamilton (D.-Ind.), but "he's got some real tests ahead of him.It doesn't take a magician to get a politician to vote for a tax cut." Friedersdorf agrees, and knows that his job will get harder when emotional issues such as busing, gun control and abortion hit the docket.

He believes that "the center of the Democratic party in Congress is moving to the right," and that votes that might once have been regarded as "defection" by the House majority leadership are now making Democrats "heroes" in districts where Reagan is popular. "But I can't afford to offend or alienate anybody on either side of the aisle, because if you lose 'em on the next one."

Always the next one, always another yellow pad of problems: "Bryce Harlow once told me that you can't stay in the White House for more than two years or you'd burn out. But he stayed for 10." If Friedersdorf remains until 1985, he will have tied Harlow's record. And beyond that, the president's man cannot see. Except that "I want to be someplace where I can have nothing above me but the sky -- all day long."