Can a 47-year-old environmentalist lawyer who looks favorably on defense budget cuts find happiness as the Congressional candidate from a working-class district that includes the Boeing Co. and suffers from high unemployment?

Surprisingly, the answer appears to be yes. With three weeks to go before an election to fill the seat vacated by Secretary of Transportation Brock Adams, Democrat Marvin Durning has emerged as the clear favorite in a district that often votes for Republicans.

The May 17 election in Washington's 7th District is the third created by President Carter's appointment of congressmen to Cabinet-level status. The Republicans won in Minnesota and the Democrats won in Georgia. Both parties are devoting resources to the Washington contest in the belief that a Republican victory here would be interpreted nationally as a sign of GOP resurgence.

The hope for that resurgence here rests on the six-foot, four-inch frame of State Sen. John E. (Jack) Cunningham, a 46-year-old businessman from the small community of Zenith who is almost unknown to Seattle voters. His strategy of winning is summed up bluntly by campaign manager Vito Chiechi, a onetime Boeing publicist.

"We're going to call Durning an environmental extremist who closes down jobs," Chechi said. "We're going to call him a hired sums of money to defend environmental causes."

A second element of the Cunningham strategy is to portray Durning as soft on defense, based on his support of President Carter's reduction in the B-1 bomber, which is partially built by Boeing. Cunningham has lumped together all the potential jobs that might be lost by Carter's proposed defense budget reductions, including jobs involved in Boeing production of the Minuteman missile in Ogden, Utah, and come up with a figure of 8,400 jobs that would be lost in the district.

On the surface, this would appear to be an attractive political strategy in a job-conscious state where new Gov. Dixy Lee Ray frequently takes a stance hostile to what she regards as environmental excesses. But in a congressional race that is more a contest between personalities than issues, the strategy has failed to ignite the Cunningham candidacy.

Durning, a hardy perennial of Washington politics, comes across as a bright, personable and somewhat disorganized campaigner who has been active in dozens of causes since he left a Yale economics professorship to become a Seattle lawyer in 1959. He is a three-time political loser who finished a strong third behind Ray and Seattle Mayor Wes Uhlman in the Democratic gubernatorial primary last September.

Political luck turned in Durning's favor when Carter named Adams to his Cabinet. Seventeen Democrats jumped into the race, including two who split the endorsements and support of organized labor. Durning, with an organization left over from the governor's race, won the nomination with 20,000 votes, slightly fewer than he had received in the district in the gubernatorial primary. The other Democrats divided 38,000 votes while Cunningham was winning 10,000 of the 17,000 votes given eight Republican candidates.

Durning is confident he will pick up a majority of the votes that went to other Democratic candidates, most of whom have endorsed him in a display of party unity. Even Gov. Ray, who rarely is on the side of Durning on the issues, has backed him.

The Democratic nominee has moved swiftly to defuse the defense issue, much in the manner that Democratic candidates accused of being soft on crime embraced the "law-and-order" issue in 1970.

Television spots now being prepared quote Durning as favoring a strong national defense. In an interview last week Durning emphasized that his father had died in the Marine Corps and that he had served in the Navy during the Korean War.

But Durning is not trying to erase his environmentalist reputation.

Despite voter rejection in 1976 of an initiative limiting nuclear power development, Washington state remains committed to an outdoors-oriented style of life.

"The reason people moved here was because of the environment," says King County prosecuting attorney Christopher T. Bayley, who is considered a liberal Republican. "They know what it's like in other places and that's what they wanted to get away from."

Another Republican, state Sen. James Matson of Yakima, believes that preservation of the environment is a political proposition accepted by nearly everyone in Washington state.

"People here have been sold - and maybe it's true - that they can have jobs and environment, too," Matson says.

This environmental axiom undercuts the thrust of Cunningham's campaign, which is hampered, too, by burgeoning Boeing employment prompted by civilian jet-transport orders. The company, which is trying its best to be cooperative with both candidates, now employs 47,000 workers in the Seattle area and expects this to increase to 51,000 by year's end.

Even though district unemployment is believed to be hovering around 10 per cent, it is far lower among heads of households, particularly male aircraft workers. Like most Republicans, Cunnigham has little reach among black voters, who have high unemployment and number about 7 per cent of the district's population.

Cunningham's own literature recognizes the importance of the environment. He takes credit for an amendment restricting the size of tankers in Puget Sound. He also supported successful efforts by the administration of former Gov. Daniel Evans to restrict the caputre of whales off Washington shores.

But the Cunningham environmental stand seems to get in the way of his own effort to portray what he calls "a clear choice" between the two candidates. As one Republican close to the campaign put it: "Jack has fuzzed the issue enough so he won't get votes from the trade unionists, who are basically Democrats. But he hasn't done enough to overcome Durning's popularity with the lakeshore liberals, who are Republican white-collar types who put the environment ahead of other issues."

There is a widespread opinion among both Democratic and Republican politicians that a more liberal Republican, such as Bayley, might have been a better choice as a GOP candidate. Durning does all he can to encourage this view, describing Cunningham as "junior Ronnie Reagan from Peoria" and praising the administration of former Republican Gov. Evans.

Cunningham decided, soon after he announced, that he would remain on the job as state legislator in Olympia more than 50 miles away. This limits his campaigning to weekends, evenings and early mornings while Durning campaigns fulltime.

And Cunningham, while considered at least as articulate as Durning on television, has proved remarkably touchy about minor points. When a Seattle reporter described him as "a wealthy businessman," Cunningham (who says he makes $50,000 a year and has a net worth of $125,000 responded with an angry denunciation. The result was a spate of stories about Cunningham's wealth, or lack of it, which diverted the focus of his campaign.

Both candidates are continuing the high-spending trend of this year's special elections; estimates are that Durning will spend $150,000 on his campaign and Cunningham with $10,000 to $20,000 less.

The Cunningham campaign has been helped by contributions, amounting to perhaps one-fourth of his total fund-raising, from such organizations as the National Conservative Political Action Committee, the Citizens for the Republican (the Reagan committee), the committee for Survival of a Free Congress, the Right to keep and Bear Arms Political Victory Fund and the Fund for the Conservative Majority Cunningham also flew to Southern California last week to have his picture taken with former President Ford and television footage shot with Reagan, but he says he is not certain whether he will use either in the campaign.

Whether or not he does. Cunningham seems to have failed to capture the political offensive with his strategy or portraying Durning as an environmental extremist who threatens Boeing jobs.

"Boeing workers like the out-of-doors," says Durning. "They like the efforts to protect outdoor recreational opportunities. That is why they live here. They want both jobs and the environment, and that seems reasonable to me."