George Herger, one of those farmers who treat visiting city slickers with polite wariness, bemusement and occasional flickers of amusement, answered a political question by telling of the local veterinarian who prescribed minimum treatment.

"Doc Korbett used to say, 'The Lord heals and the doctor takes the fee,' " Herger, a third-generation farmer here, recalled. "I don't think anyone thinks the Democrats can do anything more about the farm problem than the Republicans or that the government has the ability to change things. It can give a little help to the sick, but the problem has to heal itself."

At the fairgrounds on the other side of town, where the Benton County fair was opening, Warren Richart, the Democratic county treasurer, offered another perspective on the Nov. 4 elections.

"We Democrats ought to sweep this year, but I see they're lowering the prime interest rate and I wonder what else the administration will do in the fall," he said, looking over at the livestock display barns. "More loan payments? If people are making money in September and October it'll be good for the Republicans."

These observations illustrate the irony of the political situation this summer in the Farm Belt, which is in the fourth year of its worst economic slump since the Great Depression.

The news during those years has featured farm foreclosures, bank failures, business closings and suicides. According to a recent report of the congressional Joint Economic Committee, Iowa, one of the most richly productive agricultural areas in the world, ranks 47th among the states in annual income from wages and proprietorships. Wisconsin, with troubled farmers and high unemployment in manufacturing, is 37th, North Dakota is 34th and South Dakota is 33rd. Minnesota, with a more varied economy, is 22nd.

Democrats say the accumulated anguish here should trigger an anti-Republican rural revolt this fall that could speed them toward picking up the four seats they need to wrest control of the Senate from the GOP, help add 10-to-20 House seats nationally and protect their 2-to-1 gubernatorial advantage.

This, after all, is the home of Midwest populism, Wisconsin progressivism, the Minnesota Democrat Farmer Labor Party and the old quasi-socialist Non-Partisan League of North Dakota.

This is where, in 1932 and 1933, the National Guard was called out as farmers overturned milk trucks and slaughtered livestock on the way to market and defied foreclosures with shotguns. This is where in Le Mars, Iowa, farmers hauled a judge off the bench, took him outside, put a noose around his neck and threatened to hang him unless he promised to stop farm foreclosures. He refused and they backed down, but people still recount the incident with wonder.

There may yet be a new rebellion, as the Democrats hope, but there's not much sign of it yet. In the five upper Midwest states, four Republican Senate seats (South Dakota, Iowa, Wisconsin and North Dakota) and two Republican governorships (Iowa and South Dakota) are at stake this year. Two Democratic governors are up, Rudy Perpich in Minnesota and Anthony S. Earl in Wisconsin.

There are a number of reasons for the political state of affairs in this region:

Republican candidates generally have distanced themselves from the Reagan administration's farm policies. Rebellion has been replaced by ticket-splitting, a tradition of voting on each candidate on his or her merits.

Republican candidates also are the beneficiaries of the GOP's political successes since 1980 and the concomitant demoralization of the Democrats. There has been a Reagan Revolution of a sort out here.

While many midwesterners may still believe that the Republicans are the party of the corporations and the country club set, many also have turned away from the New Deal belief that government -- under the Democrats -- is the solution.

"We don't hear the Democrats offering any ideas that seem credible," said Tom Whitney, a Des Moines attorney and former Iowa Democratic chairman.

George Reedy, former White House press secretary to Lyndon B. Johnson and now a faculty member at Marquette University in Milwaukee, agrees.

"If you put a gun to my head, I'd bet that the incumbents will win down the line," he said. "People have the feeling that government is irrelevant to their lives, that it's not a very interesting game. This is really the end of the Roosevelt New Deal era. It's like it was back in 1932."

Paradoxically, if government acts to help farmers and small businesses here this fall, which most expect it will, it will be a Republican administration on behalf of Republican candidates. Many say they believe that government policies are the cause of farm woes, but as Herger asks, "How are a lot of people going to make it without the farm programs?"

Democrats anticipate several possible administration actions to help GOP Farm Belt candidates, particularly with control of the Senate at stake. A likely one would be an accelerated government payment schedule to farmers in the price support program that would give them full payment this fall rather than stretching it out until late in 1987 as under current regulations.

No one agrees on who's to blame, a factor that doesn't help the Democrats. Midwesterners fault the government, the bankers, crop surpluses, former president Jimmy Carter's embargo of grain sales to the Soviet Union, and each other.

"The farmers who are making money still outnumber those in serious or terminal financial trouble and many of the successful ones think a lot of those in trouble have themselves to blame," said Ed Campbell, a Des Moines real estate developer and a former Democratic state chairman.

President Reagan may be less popular here (50 percent approval rating in Iowa compared with 68 percent nationally) than in any other state in the nation, but he is still popular enough to help deflect across-the-board blame from Republicans.

"In the early 1930s Midwest farmers thought Herbert Hoover was a cold fish even though he was born in Iowa," said Wayne Rasmussen, the Agriculture Department historian. "But Reagan retains his personal popularity generally, and they haven't focused on him or any one villain." Finally, there's a widespread feeling that the farm problem may have bottomed out, that the major shocks are over and most farmers and small businesses have made their adjustments and that expectations are somewhat lower. Also, in many areas the disaster hasn't been as great as feared.

"We see a little light although we don't know how bright it is," said Floyd Schnirring, the Sac County (Iowa) extension agent. "We thought we'd lose 10 or 15 percent of our farmers in the last two years and we've only lost about 2 1/2 percent. I think most who make it through this year will come out all right."

Democrats foresee possible trouble in the fall, however. The market price for corn is dropping and another near-record crop is on the way with most of last year's crop still in storage.

"When there's a death in the family or other tragedy we know they go through the stages of shock, denial, anger and resignation," said David Nagle, the Democratic House candidate here. "Is there a fifth stage, the revenge stage? There's no evidence of it yet, but my street sense says this will crystallize in the fall. If it does, it'll be late and it'll move fast and it'll be bad news for Republicans."

The betting right now is that the Democrats have a good chance of picking up one Senate seat in the upper Midwest, that there will be no change in the governorships and that the House races generally will be a wash.

The Democrats' best prospect is the South Dakota Senate race in which Rep. Thomas A. Daschle (D) faces Sen. James Abdnor. Abdnor is personally popular, but Daschle has won two statewide races for his at-large House seat, is well-organized and financed and popular with farmers because of his aggressiveness in dealing with their problems. The Republicans are favored to hold the governorship and the Democrats will be hard-pressed to hold Daschle's House seat.

In Iowa, Sen. Charles E. Grassley (R), a shrewd, veteran politician, is favored over lawyer John Roehrick, an underfunded challenger, unless he unexpectedly self-destructs. Grassley has committed a couple of recent gaffes, including placing a $20 million tax break in the Senate tax revision bill on behalf of a trucking company.

Republican Gov. Terry E. Branstad is supported by farmers but is vulnerable to Lowell Junkins, former state Senate majority leader, because small-town businessmen, the core of Republican strength, say he hasn't done enough about their economic problems. This race is rated a toss-up but many Democrats privately fear Branstad will squeak through.

In the House races, where the Republicans hold a 4-to-2 edge, the Democrats could pick up a House seat if everything goes their way, or they could lose one.

The three Republican incumbent House members running for reelection are favored, as is Democratic Rep. Neal Smith. Television star Fred ("Love Boat") Grandy is favored to win the seat of retiring Democratic Rep. Berkley W. Bedell and there is a close, hard fight between former Democratic state chairman Nagle and Waterloo attorney John McIntee for the seat of retiring Republican Rep. Cooper Evans.

In Minnesota, Republican Reps. Vin Weber and Arlan Stangeland, who represent agricultural districts, are vulnerable because of the farm problems but are expected to pull through. So are the rest of the incumbents, including Democratic Gov. Perpich.

Weber, a leader of conservative Republican House members, has been criticized for losing contact with his district and being tardy on farm problems but he has been working the district almost round the clock. He is being challenged by Dave Johnson, a farmer who was a Reagan delegate to the Republican National Convention in 1984 but later switched parties.

"Johnson has money and some credibility problems," said a veteran Minnesota political observer. "Weber is very savvy and hard-working and is regaining lost ground."

The North Dakota Senate race could be the sleeper of the year. Republican Sen. Mark Andrews is vulnerable for a number of reasons, including resentment over a $10 million malpractice suit on behalf of his wife. His Democratic challenger, state Tax Commissioner Kent Conrad, has made substantial gains in the polls.

Sen. Robert W. Kasten Jr. (R-Wis.) also is vulnerable for personal reasons, including a drunken driving charge in the District of Columbia and a scandal involving a business partnership. Still, it's going to be hard for the Democratic challenger, as yet unselected, to unseat him.

"Kasten's working the state like Democratic Sen. William Proxmire and he's raised enough money for 1992 and 1998," said one Democratic observer.

"He's vulnerable but it's a very tough race," agreed Suellen Albrecht, the Wisconsin Democratic chairman. "The farmers are still in pretty bad shape but the state has given them some help in restructuring their loans."