ATLANTA — Businessman David Perdue has defeated longtime Rep. Jack Kingston in the Republican runoff for Georgia's U.S. Senate nomination, setting up a matchup against Democratic nominee Michelle Nunn that will help determine which party controls the Senate for the final years of the Obama administration.

Tuesday night's primary runoff win validates Perdue's campaign as an outsider. The former CEO of Reebok, Dollar General and the failed textile firm Pillowtex, Perdue offered his private sector record and tremendous wealth as proof that he can help solve the nation's ills in a Congress largely devoid of experience business titans. He spent more than $3 million of his own money blasting Kingston and other primary rivals as career politicians, including one ad depicting his rivals as crying babies.

"I've never run for anything in my life. I'm humbled," Perdue told supporters gathered at a hotel in the Buckhead neighborhood of Atlanta.

With 99 percent of the precincts reporting, Perdue led Kingston by about 8,000 votes — enough for 50.9 percent of the vote. Perdue also led Kingston in the initial May primary, but both men fell well shy of the majority necessary to win without a runoff.

Perdue won handily in Hall County, earning 59 percent of the vote.

Perdue immediately shifted to general election mode, praising Kingston and calling for party unity in the race against Nunn and Libertarian Amanda Swafford of Flowery Branch.

Republicans need six more seats to regain a Senate majority for the final two years of President Barack Obama's tenure, and the GOP cannot afford to lose retiring Sen. Saxby Chambliss' seat.

"I respect Michelle Nunn. I respect her family," Perdue said, a nod to her father, former Sen. Sam Nunn. But, Perdue added, "I will prosecute the failed record of the last six years of Barack Obama."

Across town on the Georgia Tech campus, Kingston thanked his supporters and let them know he'll be working for a Perdue win in November. "We will keep Georgia in the Republican column," he said.

As he did in May, Kingston ran up huge margins across southeast Georgia, where he's represented Georgia's 1st Congressional District since 1993. In his home Chatham County, he won 86 percent, with about 12,500 more votes than Perdue. But Perdue erased Kingston's home base advantage by running more consistently around the rest of the state, particularly in the heavily populated Atlanta and its suburbs. Perdue won Fulton County and all the surrounding counties that make up the metropolitan area.

With the win, Perdue overcame a Kingston coalition that spanned the internal GOP struggle between tea party conservatives and traditional GOP powers. Kingston ran with the endorsement and more than $2.3 million in advertising support from the U.S. Chamber of Commerce, a titan of the Washington establishment. But he also garnered backing from tea party leaders and Karen Handel, the tea party favorite who finished third in the May primary.

Kingston, 59, ran as an 11-term congressman in a year when voters have expressed widespread dissatisfaction with the nation's direction, arguing that his record proves his conservative credentials. He pitched his range of endorsements as proof of his appeal across ideological barriers.

Yet the returns suggest showed that wasn't enough to trump a political reality: Americans typically love their congressman but loathe Congress as a whole.

National Democrats view Nunn as one of their best opportunities to pick up a GOP-held seat. She's raised more than $9 million and reported $2.3 million left to spend earlier this month. Perdue reported less than $800,000, but his personal wealth ensures that his campaign doesn't have to worry about money.

Perdue's win could require a strategic shift for the new Republican nominee and his Democratic opponent, since they now can't simply run against the sitting Congress and its discord.

Nunn, an Atlanta nonprofit executive, uses her father, an old-guard Southern Democrat who served four terms, as an example of what kind of senator she'd be. She also eagerly highlights her tenure as executive of Republican former President George H.W. Bush's foundation.

Both candidates should have plenty of money. Nunn has raised more than $9 million and reported earlier this month than she had at least $2.3 million left to spend. Perdue reported less than $800,000, but he has enough personal wealth to finance his own campaign.

Outside groups have already spent more than $8 million on the race, and that continued Tuesday night. A Super PAC, Ending Spending Action Fund, ran an ad attacking Nunn as a supporter of Obama's health care law.

The fund is backed by the Ricketts family, whose patriarch, Joe Ricketts, founded TD Ameritrade and now owns the Chicago Cubs baseball team.