Former Rep. Tom Coburn won a resounding victory in Oklahoma’s Republican Senate primary Tuesday, staving off a costly runoff and setting up a November showdown with Democratic Rep. Brad Carson.

Coburn garnered 61 percent of the vote in a three-way contest with former Oklahoma City Mayor Kirk Humphreys and state Corporation Commissioner Bob Anthony.

Humphreys, the one-time frontrunner who entered the race early with the backing of the state GOP establishment, finished second with a disappointing 25 percent of the vote. Anthony, whose focused attacks on Humphreys set off a negative ad war in the closing weeks of the campaign, placed third with 13 percent.

Carson easily won the Democratic nod, taking 79 percent of the vote in his primary.

The general election contest to succeed retiring Sen. Don Nickles (R) is expected to be one of the most competitive and closely watched this fall. There are eight open-seat Senate races this cycle and Oklahoma is one of only a handful of pick-up opportunities for Democrats attempting to regain a majority in the chamber.

Republicans, however, say that Democrats have little reason to be optimistic about their chances of winning in the GOP friendly terrain.

In a statement, National Republican Senatorial Committee Chairman George Allen (Va.) expressed confidence in the party’s ability to unite behind Coburn and hold the seat in November. Nickles and Sen. James Inhofe (Okla.) were among the prominent Republicans in the state who helped to initially clear the primary field for Humphreys, whose campaign collapsed in the final two weeks of the campaign.

“Primaries by nature are competitive affairs where winners emerge tested by the experience and steeled by a hard-fought victory,” Allen said. “Dr. Coburn has been challenged and emerged victorious and stronger for it.”

Coburn, a doctor who still runs a family medical practice, served in the House from 1994 through 2000 when he honored a term-limits pledge and did not seek re-election. He has said that if elected, he will serve no more than two terms in the Senate. Carson was elected to succeed Coburn in the eastern Oklahoma district that includes Muskogee and the area known as Little Dixie.

The rural, traditionally Democratic area in and around the Tulsa media market will be a key battleground in the race between Carson and Coburn.

Coburn, who railed against wasteful spending and often bucked the GOP leadership while in the House, is expected to highlight his independence and fiscal conservatism throughout the campaign. But Republicans say his maverick image and populist appeal is likely to help him pick off conservative Democratic voters.

But Carson, a member of the conservative Blue Dog Coalition, has compiled a moderate voting record in Congress and his campaign will seek to paint Coburn as a right-wing extremist who opposed key legislation that benefits Oklahomans, including the farm bill.

Carson spokesman Brad Luna wasted little time Wednesday highlighting the differences between the two candidates on Wednesday, describing Coburn as “someone who’s on his own radical agenda.”

He predicted that voters would choose the candidate who is “not someone who’s going to go to Washington and blow up the tracks, but someone who’s going to drive the train.”

Carson raised a little more than $1 million in the second quarter of the year and had almost $2 million in the bank as of June 30.

While Coburn’s late entry into the race prompted questions about whether he could raise enough money to remain competitive, his once sluggish fundraising was boosted greatly by the Club for Growth.

The conservative, anti-tax group’s political action committee estimates that it raised $360,000 in bundled contributions for Coburn. The PAC also spent $170,000 on ads touting the former lawmaker. The group, which released a statement Wednesday claiming partial credit for Coburn’s victory, also plans to play heavily in the fall campaign.

Elsewhere in the state there were no surprises in Tuesday’s primary results. In the 2nd district race to succeed Carson, state Rep. Dan Boren won the Democratic nomination with 58 percent of the vote. Boren, the son of former Sen. David Boren (D-Okla.), beat former district attorney Kalyn Free, who was heavily backed by EMILY’s List. Free got 36 percent in the primary.

Boren is expected to cruise to victory in November over commercial horse breeder Wayland Smalley (R).

In other primary results, Rep. John Sullivan (R) easily beat back a challenge from 66-year-old businessman Bill Wortman, whose campaign was boosted by former aides and associates of the Congressman. Sullivan received a solid 70 percent of the vote.