In the early 1970s Bob Edgar was a Methodist minister from suburban Philadelphia, a do-gooder who worked on a college campus and helped set up a drop-in center for the poor. He'd never thought much about politics, but one day, he explains, "I got angry at the president of the United States."

It was the day Richard M. Nixon fired Watergate special prosecutor Archibald Cox.

No Democrat had been elected from Edgar's district since before the Civil War. But within a year, he was Congressman Edgar, the gentleman from Pennsylvania, one of a band of fiery young reformers who rode the wave of Watergate outrage into Congress.

A decade later, the Young Turks are approaching middle age. The apple-cheeked clergyman is now a politician with computerized mailing lists and Washington consultants.

The issues in Edgar's fifth congressional race this fall are not honesty or corruption, but the prosaic complexities of federal budgeting and unemployment in Delaware County.

The education of Robert W. Edgar is the story of an angry young man who stayed angry--only he got better at it. In eight years he has learned to get along in Congress without really going along.

He is a savvy enough congressman to get former vice president Walter F. Mondale to address a fund-raising luncheon for him on Mondale's arrival in Philadelphia for the Democrats' midterm conference.

"Edgar's miracle" is what they called his first victory at the polls. Ever since, the reelection of this unabashed liberal in a conservative county where Republicans outnumber Democrats almost three to one has confounded political experts.

"A healthy sense of outrage is not bad for the political process," he says. "I'm not a good wheeler-dealer. I'm thought of as one person who rattles the chains of the system."

At the outset, Edgar took two unglamorous committee assignments, Public Works and Veterans, and parlayed them into platforms for popular causes: pork barrel reform and rehabilitation of Vietnam veterans.

In Public Works, he turned the liberal's big-spender image upside down, at one point invoking a parliamentary maneuver that killed $1.4 billion worth of dams and water projects in 46 states. His colleagues were furious. His constituents loved it.

When Congress returns from its Fourth of July recess, Edgar will tackle the pork barrel again, in his annual Quixotean battle against the $3 billion Tennessee-Tombigbee Waterway, the massive canal now under construction through five southern states. Last year, he helped lead a coalition of liberals and fiscal conservatives within 10 votes of deleting funds for the project.

On the Veterans Committee, Edgar lobbied hard for storefront counseling centers for Vietnam veterans and fought successfully for continued funding despite Reagan administration cutbacks. As chairman of the education subcommittee, he is cosponsoring a broad new GI bill. Thus, while Edgar's liberal votes against defense spending caused the national Veterans of Foreign Wars to contribute to his last opponent, his local VFW supported him enthusiastically.

Four years ago, Edgar, son of a General Electric assembly line worker, ascended a national podium which is the envy of his more anonymous colleagues: chairmanship of the 212-member Northeast-Midwest Coalition, an influential group that fights the flow of federal dollars to the Sun Belt through defense contracts, energy and water projects and other programs.

With his clean-cut, choirboy looks, Edgar seems younger than his 39 years. His colleagues describe him as hardworking, decent, intense and sometimes preachy. Unexpectedly meeting some constituents in a House office building hallway, he is at a loss for small talk, uncomfortable with the glad-handing that comes naturally to many politicians.

Eight years have mellowed his style, if not his principles. "I was a male version of Bella Abzug," he confesses. "It was a while before some of my colleagues recognized that I had a sense of humor."

The walls of his office are hung with savage political cartoons. On the door is a poster of three American churchwomen murdered in El Salvador, pictured against a backdrop of dripping blood. The books on his shelf: "Managing Global Problems," "Revitalizing the Northeast," "Guns Don't Die--People Do," "Women and Social Change," "The Dancing Wu Li Masters: An Overview of the New Physics."

Across the coffee table from the congressman, the executive director of the Pennsylvania Optometric Association is complaining about the Federal Trade Commission and its investigation of contact lens practices.

Edgar, who had just sent out a newsletter highlighting his 93 percent Consumer Federation of America voting record, tried to be tactful. He was sure that Pennsylvania optometrists are entirely ethical. Perhaps the problems are in Alabama, Mississippi or other states.

At any rate, the message was clear. Edgar would not be the 181st cosponsor of a bill to curb powers of the FTC.

Afterward, Edgar sighs. "There's got to be enough joy in the issues to get you through this," he says.

Earlier, there was the luncheon of the Pennsylvania Highway Information Association, which handed out golf tees over steak. Then there were the plumbing and heating contractors from his district, wanting Edgar to sponsor a bill to use the FBI to curb union violence. He wouldn't.

Instead, he lectured the contractors about Reaganomics. "Reagan hasn't lost a battle," he tells them. "We cut domestic spending, though we didn't cut peanut subsidies or sugar subsidies. We took all $39 billion in cuts and spent $40 billion for more defense. We passed the largest tax cut in history which reduced our revenues by $37 billion. Then we took the deficit and borrowed it."

Edgar is in his element. Facts and figures. The contractors look skeptical. "I say more time. Give the president more time," says one.

Edgar admits to what he calls "issue arrogance." He relishes details of mass transit legislation, formulas for allocating veterans education assistance, intricacies of capital budgeting. Two years ago, he tried to stop a $4.4 billion water resources bill by introducing 184 amendments.

The return postcard on his fund-raising appeal reads, "Dear Bob: I would like to help you deter nuclear disaster, spur economic recovery, and build effective and compassionate government. Enclosed is my contribution of . . . . "

Predictably, environmentalists love him. "I know of no finer member of the House or the Senate," said Brent Blackwelder who has lobbied 12 years for the Environmental Policy Center. "The Public Works Committee is notorious for being in the pocket of the highway, construction and navigation lobbies. Edgar is willing to challenge all three."

More telling is the grudging admiration of his opponent, B. Joseph Tofani of the Water Resources Congress. "I don't agree with a lot of things Edgar's trying to accomplish," Tofani says. "But I'll have to say he's persistent. He comes back and back and back. He never knows when he's beaten."

This spring, working with conservative Republican Gerald B. Solomon of New York, Edgar helped pass an amendment to a $550 million bill requiring the beneficiaries of federal dams--western farmers, urban water customers--to pay part of the cost of safety repairs.

It was typical of Edgar to forge a shrewd bipartisan alliance, and let Solomon take the credit.

"Edgar does a lot of work quietly and behind the scenes," says Les Aspin (D-Wis.). "He doesn't grandstand. For instance, if I weren't on the Armed Services subcommittee that deals with the GI bill, I wouldn't know Edgar was behind it. Sonny Montgomery is the guy who's publicly out front on it. But Edgar is at all the markups. He makes phone calls every time something's happening."

G.V. (Sonny) Montgomery, the Mississippi Democrat who chairs the Veterans Committee is as conservative as Edgar is liberal. Yet he praises the Pennsylvanian for doing his homework and knowing when to compromise. "I know where he's coming from and he knows where I'm coming from and we meet pretty good in the middle," Montgomery says.

Edgar's district, a suburban county that extends from the rundown row houses of Chester to the leafy back roads of Swarthmore, was dominated for years by the War Board, a Republican version of Chicago Democratic Mayor Richard J. Daley's political machine. County jobs are still filled by patronage, so Edgar's Republican opponents "automatically start out with 3,000 volunteers," says John A. Briscoe, his chief aide.

In the past three elections, Edgar has hung on by his fingernails, making up for his liberal voting record with a good-guy image, energetic constituent service and a knack for turning issues to his advantage. This year, redistricting has given him a small Democratic area in Philadelphia, but it is outweighed by the addition of several rock-ribbed Republican areas to the north.

Lacking a strong party organization, Edgar has created his own constituencies--environmentalists, women, veterans, Social Security recipients, union members. He peppers them with newsletters and targeted mailings, using computerized lists.

No one invites him to cut ribbons, so he generates events. Twelve thousand Delaware County businessmen, for instance, were invited to attend a day-long export conference in April "sponsored by Congressman Bob Edgar and the U.S. Department of Commerce." Earlier, he had organized another conference to advise them on how to bid for federal contracts. While battling federal pork nationwide, Edgar, having commissioned a poll that shows jobs to be a big issue in his district, takes credit for helping a Chester firm compete for renovation of the battleship Iowa. "Defense spending in Delaware County alone will increase by 61 percent in 1982," Edgar reports in his latest newsletter, adding, however, that defense outlays create fewer jobs than social spending.

Mass transit is one of Edgar's principal interests. He has introduced legislation to fund maintenance of existing systems. And mass transit, as it happens, is not only a good liberal cause, it is a good political issue in a district largely served by public transportation.

Amid the politicking, Edgar walks the line between idealism and pragmatism. One recent day back home, he startled a Chamber of Commerce breakfast by advising his audience of Republicans that he ranks eighth among 435 members of Congress in opposing President Reagan. He stopped by his campaign office to jolly up the volunteers. He gave his Reaganomics critique at an Arco plant. He met with editorial writers at the Philadelphia Inquirer and told them about the dam safety amendment. He bowed his head and prayed at a memorial service of Gold Star mothers, and then admonished one of the white-gloved matrons who complained about welfare recipients to be "compassionate."

As if to keep himself pure, Edgar has vowed to quit the House after 12 years, but he doesn't rule out running for statewide office. "If I wanted to get elected by 30,000 votes in Delaware County," he muses at one point, "all I'd have to do would be to commission a poll and be a nice guy on those issues. And in Washington, I could keep quiet on the coal slurry pipeline and get four or five lobby groups to make contributions to my campaign."

But, in a way, the angry young man is still the minister. "I learned my politics in the church," he says. "I have a mission to change things. I think of myself as a teacher of people rather than just a public official."