ROCHESTER, MINN., NOV. 2 -- When it comes to running for reelection, Sen. Rudy Boschwitz (R-Minn.) wrote the book.

How should a candidate work a county fair? "Stop every 100 yards and conspicuously wipe the sweat off your brow," he advised fellow GOP senators in a breezy how-to memo he wrote following his landslide 1984 reelection. What about fund-rasing? "Nobody in politics {except me!} likes to raise money." Speeches? "Give very few speeches." Endorsements? "The president -- you have to have him!"

This year, Boschwitz has been faithful to his own advice. He has made lots more fairs than speeches. He has outspent his opponent 7 to 1. He had President Bush here stumping for him today, the second presidential visit in five weeks.

But he is also in danger of becoming the most surprising victim of the anti-politics of 1990. Boschwitz is in a dead heat with the most unconventional of this year's crop of challengers -- Paul Wellstone, 46, a political scientist at Carleton College and community organizer whose campaign evokes the peace-love-and-justice flavor of the 1960s counterculture.

"Boschwitz's problem is that he is running an orthodox campaign in an unorthodox year," said David Lillehaug, a Wellstone adviser.

Unorthodox is the gentlest way to describe Minnesota politics this year. Last weekend, the Republican gubernatorial nominee, Jon Grunseth, dropped out of the race following allegations of sexual misconduct. This summer, Sen. Dave Durenburger (R-Minn.) became the ninth senator in history to be formally denounced by his colleagues, who cited him for abusing honoraria and travel expense rules. Meantime, Rep. Arlan Stangeland (R-Minn.) is fighting for his political life following disclosures that he made hundreds of phone calls at taxpayer expense to a female lobbyist.

Boschwitz, 59, a genial businessman who founded a chain of plywood stores, is personally untainted, but he ruefully notes: "Politics hasn't exactly been showered in glory in this state this year, and all of us who are in office have suffered."

He also has taken on another burden: Boschwitz is one of the few candidates who has decided to wear Washington on his sleeve this fall. Before Bush came to town, Sens. Pete Domenici (R-N.M.) and Robert J. Dole (R-Kan.) also were in the state for Boschwitz, praising him as the only senator in a tight race who voted for the federal budget deficit-reduction package.

Wellstone has joined Democratic challengers around the country in using the budget deficit debate to portray the Republicans as the party of the rich. But the core of his appeal goes deeper.

He has spent the year making Boschwitz's huge war chest ($7 million) and the incumbent's alleged coziness with political action committees (PACs) a metaphor for special interest politics gone amok. One of Wellstone's ads shows a child writing out a zillion-dollar check to Boschwitz. "Maybe then he'll listen to them," a narrator says.

"I've had to jujitsu the money," explained Wellstone, a former champion college wrestler in the the 126-pound class -- meaning he had to find a way to turn the weight of the incumbent's dollars against him.

Wellstone, who tells audiences he will be a "rock-the-boat" senator, wrote his doctoral dissertation on black militants. He spent the past decade doing community organizing for causes that include the homeless, the family farmer, the nuclear freeze and the Central American peace movement. He was arrested in 1970 at an anti-Vietnam War protest and in 1986 at a farm foreclosure protest. In 1988, he co-chaired Jesse L. Jackson's presidential campaign in Minnesota.

This year, he has been stumping for votes in a green-and-white bus that looks like a relic from the 1960s, and his funny, offbeat television ads all play off the David vs. Goliath theme. In one, he races through a 30-second bio, explaning that he does not have much money so he has to jam everything in.

Until a few weeks ago, his campaign struck most observers here as charming, creative -- and utterly quixotic. Then, almost overnight, polls showed him narrowing a 15-point gap to a virtual tie. Last weekend, the state's two largest newspapers, the Minneapolis Star-Tribune and the St. Paul Pioneer Press, endorsed him.

Some ascribe the sudden shift to the nationwide emergence of the tax fairness issue. "Minnesota's progressive, populist roots are reestablishing themselves this fall," said Wayne Cox, state director of the Citizens for Tax Justice.

But for those who think populist economic themes play best in bad times, Minnesota seems an unlikely stage. It has one of the healthiest economies in the nation -- the unemployment rate here is below the national average, and the state government is sitting on a surplus.

"I'm not comfortable reading this as a populist surge," said Paul Light, associate dean of the University of Minnesota's Humphrey Institute. "There's been so much noise from the soap opera of the governor's race, I'm not sure how much of Wellstone's message has gotten through."

Enough has gotten through that Boschwitz is closing the campaign with a battery of television ads that allege that Wellstone's call for national health insurance and other domestic spending proposals would triple the national debt and double the tax burden on the middle class. "He says the rich would foot the bill," one ad says. "Trouble is, he thinks you're rich."

Bush made a similar point at a rally at a high school here, but Wellstone, by now a practiced political guerrilla, was ready. He held a news conference here just before Air Force One landed. "I think the contrast is pretty clear," he said. "Big jet. Our bus. Big wigs coming from Washington -- the very people who have been there during this mess, coming in now. I campaign on my own . . . I don't mind the contrast at all."