A group of businessmen went to see Rep. James M. Shannon in this Lawrence, Mass., office the other day about a multibillion-dollar jobs program that President Reagan has targeted for extinction. They were there to defend the program because their companies -- small high-technology firms in the bustling Merrimack Valley -- get job-training funds from it.

The irony was not lost on Shannon, a Democrat who has taken heat from the business community for his liberal voting record. He'll vote to jettison the jobs program because it's the only way in a tight federal budget to save nutrition and other programs that he values even more, he told them.

"There's no free lunch," Shannon explained tartly.

Not long ago it would have seemed preposterous for a 29-year-old liberal Democratic congressman to lecture a group of conservative, largely Republican businessmen on the myth of a "free lunch" and the expendability of a major social welfare program.

But Reagan and his campaign to cut the budget have radically altered the political landscape, twisting some of the old familiar patterns beyond recognition -- at least for the time being.

Even lawmakers like Shannon, who proudly continue to call themselves "liberal Democrats," have become economizers. But there are also gnawing misgivings about the budget cuts, even among Reagan loyalists.

Like many of his colleagues, Shannon went home for the Easter recess, observing a ritual of town hall meetings, main street strolls and plant visits that have become an integral part of the legislative process. During the recess ritual, members show the flag, renew old ties with constituents and, perhaps most importantly, test the winds on issues they will face when they return to Washington.

When Congress resumes work today, the first and biggest test will be tyhe proposed spending targets for fiscal 1982, including targets for fiscal 1982, including a White House-blessed "bipartisan" version of Reagan's proposed budget cuts and less drastic Democratic alternative drafted by the House Budget Committee. The House is scheduled to take up the package later this week. Judging by some predictions voiced two weeks ago, the recess pressures could well be decisive.

To get some idea of these pressures, and how members are responding to them, Washington Post reporters joined five House members in their districts during the recess: Reps. Kent R. Hance (D-Tex.), Glenn M. Anderson (D-Calf.), Al Swift (D-Wash.), Jim Leach (R-Iowa) and Shannon. The focus was on Democrats because they hold a majority in the House and because Reagan cannot win without support from at least some Democrats.

Out of all the tugging of coatsleeves back home came some clear impressions.

Reagan has already won most of his budget battle is well-positioned to win more. But there is strong, mounting opposition to some specific cuts. And the full impact of thesef and other cuts has yet to sink in. Some members have the haunting feeling that the cuts that are praised by citizens now may be damned later. So the representatives intend to hedge their bets, noting that this week's vote won't be the final word on spending.

Reagan has won because mainstream Democrats like Shannon and Swift are prepared to vote for a budget -- the Budget Committee draft -- that gives Reagan 75 percent of the cuts he wants. Win or lose, it provides them with a political refuge, enabling them to appear more generous than Reagan while voting for a budget that they would have condemned as Draconian in any other year.

"There's no way we're going to significantly reduce the size of those cuts," said Rep. Swift last week as he mingled with school officials, hospital administrators, community action workers and otehrs in his Pacific Northwest district. "The public, by and large, wants them. This [the Budget Commisste proposal] makes them a little easier to take, a little more fair and equitable. It is something I can support, the best We're going to get and a hell of a lot better than I though we were going to get."

But it is not, he noted, the kind of budget that "one normally expects to come out of Democrats."

Moreover, if Rep. Hance and his Democratic colleagaues, Reps. Charles E. Stenholm and Jack Highpower are any indication, the president has a good chance of winning the votes of many conservative Democrats, enough to demonstrate conservative control of the House.

During the recess, the three Texans were repeatedly and pointedly reminded that they cannot afford to vote against Reaganhs budget.

Hance got the point at a town hall meeting in Lubbock when a constituent rose and asked, "Are you and your colleagues aware that the 1980 election was no fluke and that it's here to stay?"

Stenholm got the point, too, when he suggested that he might have cut the budget differently than Reagan did. A constituent responded: "But you're not the president."

Hance has tallied mail from his district, and it runs 690 in favor of Reagan's economic program and about 30 against. Stenholm similar support in their districts.

When Reagan phoned last Tuesday as part of his campaign to lobby conservative Democrats on the budget vote, Hightower assured him: to waste your time on me."

In the strong, almost emotional tide running in favor of Reagan's effort to cut the budget, even Democrats shy away from harsh criticism.

Longtime political survivors like Rep. Anderson of Harabor City, Calif., who represents a district that is generally working-class Democratic, walk a tightrope. "I don't want my remarks to sound critical of the president because I am not critical of his program," the seven-term Southern California congressman told a Rotary Club in San Pedro the other day. "I hope in general it is adopted, but I think there are some things that require some finessing."

But there are also potent pockets of opposition to specific spending cuts, and some members of Congress thing the opposition to growing.

Shannon is now getting as many as 100 pieces of mail a day, ranging from wards of programmed postacards complaining about school lunch cuts to streams of more spontaneous letters ojecting to cutbacks in college student loans.

Hospital administrators are working on Swift of Bellingham, Wash., to oppose some of the proposed Medicaid funding cuts.

A number of major national organizations, such as rural electric cooperatives and groups representing retarded persons, have put out the word, spawining grass-roots lobbying in member's home districts. But programs that lack vocal, well-organized constituencies are becoming orphans.

Sometimes local people aren't even aware that a particular program has been targeted for reduction or elimination. Or they don't fully appreciate the dimension of the proposed cut. In any case, the full impact won't be felt in most cases for months. "They just can't believe it is really going to happen," said Swift. An aide to Rep. Leach in Iowa said farmers don't fully realize how much farmers home loan programs are being cut. In Massachusetts, a social worker said the elderly don't know how deeply housing subsidies are being reduced.

The proposed cuts are so numerous that not even congressmen have caught up with all of them yet. For instance, until he was told by a state director, Shannon wasn't aware that a program serving several hundred children of migrant workers in his district will be cut and folded into a catchall block grant.

Leach, although he is a Republican committed to the Reagan program, personifies the ambivalence of many members about the proposed cuts -- and the political hedging that is going on all over the country. His Iowa constituents are critics of government but also its beneficiaries.

"I assure you, these are liability votes no matter which way you go," said the 39-year-old former Foreign Service officer and anti-poverty official who is a member of the GOP's moderate minority.

Item: The president of the Scott County (Iowa) Bar Association calls on Leach to help save the Legal Services Corp. from Reagan's budget ax. Leach is sympathetic. A decade ago, as an aide to Donald Rumsfeld, President Nixon's anti-poverty director, Leach helped fend off attacks on the program from other Republicans, including the governor of California, Ronald Reagan.

"Are you going to be forced to choose between the party line and individual support for the program?" Leach is asked by Hobert, executive director of the Davenport legal aid program.

"I don't know," Leach responds. "I don't know what choices we're going to have on the House floor."

Item: Leach is taken to lunch by a prominent Davenport physician and an official of the locally based John Deere Co. Their concern is Reagan's proposal to phase out professional standards review organizations (PSROs), local medical boards set up under federal auspices to help review medicla practices and hold down costs. John Deere cares because it wants to hold down costs of medical services that it is obligated to provide in its contract with the United Auto Workers.

The visitors urge Leach to help preserve the program until some workable alternative can be found. Leach indicates he will.

Item: Leach speaks to a high school government class in the small town of Vinton, where senior Denise Inman pleads politely for the college student loan program that Reagan would cut.

"A lot of kids had really planned on hopefully getting student loans," she tells her congressman. The basically middle-class program is big in Leach's district of thriving farms and farm-implement manufacturing plants -- and the University of Iowa. Leach sympathizes and says he wants to preserve the loans.

But, for the time being, he's locked into Reagan's program. His Republican constituency would be sorely offended if he weren't. He has an object lesson close at hand: freshman Sen. Charles E. Grassley, who was one of three Republicans on the Senate Budget Committee to vote this month against Reagan's budget because its projected deficits were too high. Many Iowans didn't think much of Grassley's performance.

"He sure is operating differently than he did around here," grumbled a Vinton auto dealer to Leach.

As for the future, Leach consoles himself with the fact that programs endangered by the first budget resolution (which sets spending targets and instructs committees to cut programs in line with budget goals) may get another shot in later legislation.

"The legal services battle is the battle of the summer," when legislation to extend that program is expected to come up, Leach observed last week. "In the four years I've been in Congress," he noted, "the second budget resolution has always been larger than the first."

Maybe so, but Shannon isn't holding out much hope for the Massachusetts businessman who have grown to love that favorite punching bag of conservatives, the Comprehensive Education and Training Act. In the Lawrence area, communities have used CETA public service jobs money for training workers in private businesses, especially small and struggling electronics firms that find it hard to compete for skilled workers with the hightech giants. As a result, local businessmen like CETA a lot more than their colleagues elsewhere do.

When a delegation of them visited Shannon last week, they got a bracing splash of cold water.

"I understand the importance of CETA," he told them. "I'd love to have heard this a year ago when I was taking all the heat. All i ever got for supporting CETA was criticism."

Three thousand miles away, Swift delivers a similar message to a group of school superintendents who are worried about Reagan's cuts in "impact aid" for schools. Every president since Eisenhower has tried to cut that program, and every time Congress has said no.

"Sure we're going to fight it, as we always have in the past," Swift told the superintendents. "And we've always won in the past. But this isn't the past."