A huge poster in the tiny office of the Chamber of Commerce on Main Street here proclaims proudly that "This is Paul Bunyan Country." But in the politiking for Tuesday's special congressional election in Minnesota's northwestern corner, most attention has been focused on another local giant.

"This is Bob Bergland country," says Doug St. Onge, a state legislator and local leader of the Democrat-Farmer-Labor (DFL) Party.

"It's not a particularly strong Democratic district, but Bergland won big here because the voters loved him. He was an average North Country farmer, and a very warm person. He is one of the best-liked people in Minnesota."

The central question in the election to fill the seat Bergland left last month when he became Secretary of Agriculture is whether Bergland can transfer his personal popularity to his protege, Mike Sullivan, who three weeks ago won a four-way primary race for the DLF nomination.

Sullivan, 35, is campaigning almost exclusively on coattails. His slogan, "In the Bergland tradition," is the central feature of his posters and advertisements. Bergland has been here twice on Sullivan campaign forays, and other DFL leaders, including Vice President Mondale, have also stumped the district for the party's nominee.

Yet the energetic young candidate has problems.

Although he grew up on a farm in the district, Sullivan has not lived here since the early 1960s. He left farming to become a teacher in Minneapolis, and has spent most of the last six years in Washington as a staff aide to Bergland and in Mondale's Senate office.

The Republican candiate, Arian Stangeland, presents a clear contrast to Sullivan's image as an outsider.

Stangeland has spent his life on farm in Barnesville, Minn., and likes to remind the voters that he left the district only to travel to Minneapolis during his four terms in the state legislature.

As a working farmer, Norwegian American, a Lutheran deacon and a father of seve, Stangeland would seem the ideal candidate for this sprawling rural district.

That has given local and national Republican strategists some hope that their party might prevail despite Sullivan's close association with Bergland.

Russ Evans, of the Republican Congressional Campaign Committee in Washington, says the Minnesota race is the party's best bet to pick up one of the three congressional seats left vacant by President Carter's Cabinet appointments.

"Atlanta [the former district of U.N. Ambassador Andrew Young] and Seattle [home of Transportation Secretary Brock Adams] are pratically unwinable for Republicans," Evans says.

"In Bergland's district, we're the underdogs but we've got a chance."

Local and national Republican parties have gathered $100,000 for Stangeland's campaign.

On election day, Stangeland says, "We're going to have every four-wheel-drive truck and snowmobile we can lay our hands on to get people down to the ballot."

Sullivan, in contrast, says his campaign is "having some trouble with get-out-the-vote. We didn't get that organized very well."

Sullivan expects to spend about $80,000 on the campaign, most of it targeted for advertising.

The district, which covers the entire northwest quarter of the state, comprises two different worlds.

In the west, along the North Dakota border, it is a vast, flat table of feed grain and sugar beet fields. To the east are rolling hills and sylvan lakes, where the reveries of the ice fisherman are interrupted only by the screech of sawmills and the bark of a hunter's rifle.

Stangeland thinks the voters' independent streak will work to his advantage Tuesday. "Basically, the DFL has picked a political professional from Washington and told the people here that they should like him," Stangeland says.

Some newspaper and radio editorials here reflect that feeling. "If Mike Sullivan is that great," said an editorial on station KDLM, in Detroit Lakes, "you'd think they'd trust him to run his own campaign."

Sullivan, for his part, says the endorsements from the party hierarchy can only help. like Bob Bergland ad Fritz Mondale are supporting my candidacy," he tells the voters.

In style, at least, Stangeland would seem to be the candidate closet to the Bergland model. Like the former congressman, he is a quiet, passive individual whodoes more listening than talking when he meets with voters.

Sullivan is all youthful vigor, a fast-talking fountains of statistics and bill numbers. The rhythm of his speech and his jutting index finger reminds some voters of the Kennedy brothers, which is not necessarily a political asset here.

In his campaign appearances, Sullivan is an inveterate name-dropper.

When a voter asked about housing for the elderly, Sullivan said he had "just placed a call to Patricia Roberts Harris at the Housing Department in Washington" to get federal action. He tells every campaign audience that Rep. Thomas S. Foley, (D-Wash.), chairman of the House Agriculture Committee, has promised him a seat on the committee if he wins the election.

Although Stangeland had a conservative record in the legislature, and Sullivan seems to fit the liberal mold of Mondale and Sen. Hubert H. Humphrey (D-Minn.), the candidates have not differed greatly on the issues that are important here.

Both strenuously oppose abortion and gun control. Both favor higher agricultural price supports, and both complain that federal farm insurance programs are inadequate.

Mondale insisted during his visit here Friday that "this election comes too early to be tested of the popularity of the Carter administration." But the two candidates both think Carter's presence in the White House will affect the voting.

"I lost my seat in the legislature in '74 because of Watergate," Stangeland says. "Don't tell me the President doesn't influence politics out here in the country."

Sullivan says Carter's performance to date should be a considerable asset to his campaign.

"There's a whole new spirit, a really optimistic feeling out here because of the new administration," Sullivan says. "I think that's going to help any Democratic candidate."