Democratic hopes of taking over control of the Senate were not exactly dashed this week with the discovery of Sen. Rudy Boschwitz's confidential advice to his GOP colleagues facing reelection. In a nutshell, his formula for 1986 calls for lots of state fairs, root-beer milk, good play-acting and a barrel of money.

Issues didn't appear to be one of the Minnesota Republican's priorities in a letter that has been the talk of Capitol Hill since The Wall Street Journal published excerpts from it on Thursday.

"Senator Boschwitz is the P.T. Barnum of the Republican Party," said David Johnson, executive director of the Democratic Senatorial Campaign Committee. "He thinks there's a sucker born every minute. But good politics is more than that."

"It's the perfect prescription for the percentage politician," said Christopher Matthews, spokesman for House Speaker Thomas P. O'Neill. "No wonder so many Republican senators look like pharmacists."

Some Boschwitz tips

* "Parades -- are great. Take your spouse. Walk behind your car; don't ride. Rush over and shake some hands at the curb. Stop every 100 yards and conspicuously wipe the sweat off your brow."

* "Give very few speeches," the memo advised, noting that Boschwitz avoided them "except to high schools, who would assemble 500-800 kids, and I'd be in and out in an hour (no reception, cocktails, etc.) . . . Campaign wholesale at gates to state fairs, or get to sporting events, plant gates. Walk the beaches."

* "The Minnesota State Fair is BIG doings. I'm there every year, and this was the second year of Rudy's SUPER DUPER MILKHOUSE. Don't snicker . . .We sold upwards of 200,000 glasses of milk (root-beer was the favorite flavor . . .)"

* "I wouldn't release my tax returns . . . You'll be attacked, and if you're a businessman, conflict-of-interest will be alleged due to some of your votes; and if you hold any stock, your votes and PAC money will be tied to that ownership, too (one of the reasons I didn't make my tax returns public). It's just plain unpleasant, and the press loves it. It is vital that attacks not go unanswered. That's when your paid consultants really earn their fees."

* "The president -- you have to have him! Unless, of course, you don't want to raise money. $1,000 per person gets a picture with the chief (signed), a reception (where the picture is taken), and dinner. $500 is dinner only. Important: Negotiating with the White House is not easy."

"I wouldn't argue with that," said Lee Atwater, a Republican consultant who was deputy chairman of the Reagan-Bush reelection effort. "We were tough to negotiate with. I think the problem with that event was that they needed to have 450 pictures with the president. But a good time was had by all . . . I've never heard of root-beer-flavored milk."

The private letter also urges incumbents to disregard media criticism about large financial contributions.

"Nobody in politics (except me!) likes to raise money, so I thought the best way of discouraging the toughest opponents from running was to have a few dollars in the sock . . ." it said.

"You'll get articles written about your fund-raising (the press is consumed by money in politics) . . . I raised $6 million plus and got three or four (maybe even five) stories and cartoons that irked me and lots of questions from outlying (and metropolitan) journalists . . . In retrospect, I'm glad I had the money."

The senator's press secretary, Mary Lahr, said Boschwitz sent the letter to a "handful" of his colleagues in response to requests for advice. She said he was not embarrassed by publication of the letter. "No, we're not embarrassed at all," she said. "You'd have to know Rudy . . ."

"He does run a very corny campaign," said Bill Salisbury, a political reporter for the St. Paul Pioneer Press and Dispatch. "I don't recall him wiping the sweat off his brow, but the memo certainly reflects his attitude toward the press and the electorate."

Generally, the memo seemed to generate more snickers than sobriety, although the senator does know of what he speaks. He won reelection for his second term last fall with 58 percent of the vote after outspending his opponent nearly 4 to 1.

But as budget battles loomed from Washington to St. Paul this week, not many could muster the energy to take the memo all that seriously.

"What he forgot to advise," noted Republican Sen. Bill Cohen of Maine, "is how a candidate should not walk too close behind a horse."

Said a top GOP strategist: "It is ridiculously hokey. If we had sent that thing, we would have been laughed off the street."

"Not everybody has the chutzpah to run like Rudy," said Gerry Nelson, spokesman for Minnesota's Democratic Gov. Rudy Perpich. "But anyone who takes the memo lightly does so at his own risk."

"I guess it did work for him," says Joan Growe, Boschwitz's opponent in the past election. "And you know, it's rather ironical that he tried to portray me as mean. This makes him look like the most cynical politician that ever lived."