Former three-term Rep. Tom Coburn (search) won the Republican nomination Tuesday for the seat of GOP Sen. Don Nickles (search), trouncing a popular former mayor after a bruising and expensive campaign marked by allegations of backstabbing and shady land deals.

Coburn will meet Democratic Rep. Brad Carson (search) in November in a race that could play a big role in who controls the Senate. Oklahoma is one of only a few states with open Senate seats this year, and Democrats are optimistic Carson can win in November despite the state's GOP leanings.

Nickles is retiring after four terms and 24 years in the Senate.

With all but one precinct reporting, Coburn had 61 percent, or 145,499 votes, while former Oklahoma City Mayor Kirk Humphreys had 25 percent, or 59,806 votes. State Corporation Commissioner Bob Anthony was third with 12 percent.

Carson easily won the Democratic primary with 79 percent of the vote. His closest competitor was beleaguered Insurance Commissioner Carroll Fisher, who is fighting criminal charges and an impeachment inquiry over his handling of state funds and a charity.

Coburn, a doctor, was known as a maverick and a conservative in Congress, and in 1997 helped lead a revolt against then-GOP House Speaker Newt Gingrich. Carson, the only Democrat in the state's congressional delegation, is a moderate who supports gun rights, the death penalty and the war in Iraq.

Carson immediately looked toward the November race, arguing Coburn hurt the state with his zeal for restraining federal spending. He said it will be a campaign of "stark contrast between different visions for Oklahoma. I've used my seat in Congress to benefit the people I've represented. That's something Tom Coburn has chosen not to do."

Coburn said he is ready to take on Carson and for Republicans to unify after the bitter primary. He said Oklahomans took to his conservative message that condemned pork-barrel spending and called for a balanced budget.

"The people are going to get a real good choice," he said. "It's black and white. I'm someone who has voted conservative, acted conservative and is conservative. I'm running against somebody that wants to act that way, but doesn't vote that way and isn't that way."

The defeat marked a stunning turn of events for Humphreys, who was annointed the early favorite after winning endorsements from Republicans including Sen. Jim Inhofe and former Rep. J.C. Watts.

But Humphreys saw his poll numbers dip after a barrage of ads in which Anthony questioned land sales he made several years ago.

Coburn and Humphreys had taken a pledge not to go negative, but Humphreys said he was forced to go on the offensive after the attacks from Anthony. Coburn accused Humphreys of going back on his word.

The attacks grew so intense that Nickles himself had to ask participants to cool it.

Humphreys said he was done in by Anthony, whom he called "a cut and slash guy."

"Tom Coburn is a wonderful man, but Bob did his dirty work for him," Humphreys said. "Coburn would be hard to beat on a level playing field, but it was not a level playing field."

State Rep. Dan Boren, the son of a former governor and senator, won the Democratic race to replace Carson.