Andy Ewing, retiring Rep. Tom Coburn's hand-picked successor, beat six other GOP candidates Tuesday in a primary in a district where Republicans are outnumbered 5-to-2.
Democrats split their vote, sending two candidates to a Sept. 19 runoff and the chance to regain the eastern Oklahoma seat held by their party until 1994.
Elsewhere, incumbents easily won their nominations in primaries in Wyoming and Alaska - if they even faced a challenge. But in Selma, Ala., the mayor of 36 years, a former white segregationist, was forced into a runoff.
In Oklahoma, Ewing, a soft-spoken 62-year-old known for local commercials for the Muskogee car dealership he once owned, won 60 percent of the vote in a crowded race that many thought might force a runoff.
Ewing said he plans to run a positive campaign based on serving as a "citizen legislator," just like Coburn, who kept a campaign promise to retire after three terms.
"It makes no difference to me if it's a Democratic initiative or a Republican initiative," he said, "if it's right, it's right and if it's wrong, it's wrong."
Ewing faces the winner of a runoff between state Rep. Bill Settle, 62, and Brad Carson, a 33-year-old attorney.
In another district, state Rep. Randy Beutler, 30, received 69 percent of the vote to defeat retired Oklahoma City educator Bob Mooneyham, 62. Beutler will face Rep. Frank Lucas, a Republican who was unopposed.
Oklahoma voters also advanced three incumbent GOP congressmen to the November election and approved by a margin of 4-1 a referendum to lower the cost of car tags, cutting taxes by $22.3 million.
Reps. J.C. Watts, Ernest Istook and Steve Largent easily defeated inexperienced and underfunded GOP challengers. Each faces opposition in the fall.
In Wyoming, first-term GOP Sen. Craig Thomas faced no primary opposition. Mine worker Mel Logan beat a retired businessman for the Democratic nomination to challenge Thomas in the fall.
Three-term Wyoming Rep. Barbara Cubin easily won her nomination against two poorly funded fellow Republican challengers. She will face office clerk Michael Green, who won the Democratic nomination.
Alaska's lone House member, GOP Rep. Don Young, had no challengers for his party's nomination. He has represented the state since 1973.
In a municipal election in Selma, Ala., longtime Mayor Joe Smitherman, who was in office during the civil rights violence of 1965, will face businessman James Perkins Jr., who is black, in a Sept. 12 runoff.