In an exceptional political coup, a founder of one of the most influential Washington lobbying firms won the Republican Party's endorsement for the GOP Senate nomination in North Dakota on March 6 despite the fact that he is virtually unknown in the state and, until recently, had been a Washington area resident since 1965.

Gene Knorr, who helped organize the firm of Charls E. Walker Associates in 1973, conducted a lobbying campaign unprecedented in North Dakota politics to win, 572 to 414, the party endorsement on a second ballot, defeating the the majority leader of the state Senate.

The endorsement, gained at a convention in Minot, virtually guarantees the GOP nomination. Assuming, as most everyone does, that no opposition emerges for the June primary, Knorr, 41, will face Democratic Sen. Quentin N. Burdick, 73, the incumbent since 1960, in the Nov. 2 general election.

Throughout the campaign for convention delegates, Knorr downplayed his connections with the lobbying firm and described himself instead as an "economic consultant" and stressed his government service in the Treasury Department during the Nixon and Ford administrations.

Outspending his opponent 5 to 1--$40,000 to $8,000--Knorr capitalized on the fact that in North Dakota the key to victory is not the statewide primary but gaining the support of the relatively small group of 1,000 or so party activists who attend the GOP endorsement convention.

Dick Dobson, who writes the Prairie Perspective column for the Minot Daily News, said, "Knorr put together the most impressive preconvention campaign this state has ever seen . . . . Actually it was more than incredible; it was semi-miraculous."

"For those who say it was miraculous," Knorr said in a telephone interview, "it was a heck of a lot of work."

He said he was able to counter charges that he was an outsider by telling people he has returned to the state often during his time in Washington and by arguing that his Washington experience will prove valuable if he is elected to the Senate. He said he moved his residence from the Washington area to North Dakota either in the middle or latter half of last year.

Defying GOP party leaders who told him he should move back to the state and start at the bottom, running for the state legislature, Knorr began last July to seek out Republican delegates from the 53 legislative districts who attended the state's 1980 convention. This group made up about 65 to 70 percent of those at this year's convention.

He criss-crossed the state for five months by snowmobile and pickup truck and in his family's airplane, stressing his roots in the state and his ties to the Reagan administration's economic program.

And, to take the edge off any charges of carpetbagging, Knorr ran television commercials in November and December last year showing him in a cowboy hat at his family's farm, although the tactic was dropped because the expense was not justified while the targets of the campaign were the prospective delegates, not the entire state.

Once the 1982 delegates were selected, not only did he continue personal contacts, but also he sent out five mailings.

The man Knorr defeated, David Nething, who thought he would win hands-down by calling for support from GOP loyalists, remains stunned, although he has endorsed Knorr. "For North Dakota, this is historically surprising," Nething said. "The Senate nominee has not been in the state for 18 or 20 years."

Nething credited Knorr's victory to his ability to convince farmers in the state that "he's a farmer and a rancher."

"Gene's everyday dress is, you might say, western wear," Jeff Lesmeister, the campaign manager, said. "Gene is very comfortable in a cowboy hat."

Knorr has retained an interest in the family farm and ranch operation, but since 1965 he has resided in the Washington area. He started working in Washington as an aide to then-Rep. Thomas Kleppe (R-N.D.), and then went to work for the Treasury Department as a lobbyist on Capitol Hill in 1969.

In 1973, Walker "asked him if would would like to join as a co-founder" of Charls E. Walker Associates, a firm that has since gained a collection of prestigious clients including AT&T, the Business Roundtable, Bechtel Power Corp., Bethlehem Steel, FMC Corp., Ford, General Electric and Standard Oil Co. of Ohio.

His campaign literature listed the government work, but skipped over the lobbying role, describing his recent work has having had "the honor and privilege of serving as an adviser to President Reagan's task force on economic policy," apparently referring to assistance he provided Walker, who was chairman of the task force.

In a mailing to voters, Knorr described himself as "a fourth-generation North Dakotan, born and raised on the family farm near Sawyer . . . . Dad is trying to retire now, so the varied tasks of running the operation are divided among sons Bob, Paul, Mark and myself. Younger brother Mark gets his ulcers when a spring blizzard hits during calving. I get mine when inflation hits our input costs and market prices don't cover the cost of production."