Republicans were engaged in a heated five-way primary that included Georgia Reps. Phil Gingrey (R), Jack Kingston (R), Paul Broun (R), former Georgia Secretary of State Karen Handel (R) and businessman David Perdue.
Nunn and the Republican nominee will face off in the general election.
The Huffington Post's Amanda Terkel and Samantha Lachman reported on the crowded Republican primary on Monday:
Six main candidates are vying for the Republican nomination to fill the seat of retiring Sen. Saxby Chambliss (R-Ga.). The winner will take on Democrat Michelle Nunn, who doesn't face a serious primary challenge. The two tea party candidates, Reps. Paul Broun (R-Ga.) and Phil Gingrey (R-Ga.), haven't caught fire as many conservatives -- and Democrats -- would have liked, and they're currently polling at the bottom of the field. Instead, Rep. Jack Kingston (R-Ga.) and businessman David Perdue, who have more backing from the establishment, are leading the pack. As Perdue has risen in the polls in recent days, he's increasingly come under attack from his rivals. He has been on the defensive, trying to prove his conservative credentials after saying that the government needs to increase revenue in addition to cutting spending. Former Georgia Secretary of State Karen Handel has picked up the support of some social conservatives such as former GOP presidential candidate Rick Santorum, who endorsed her last week. She had a high-profile battle with Susan G. Komen for the Cure in 2012, when it became public that she pressured the organization to stop giving grants to Planned Parenthood. Patent attorney Art Gardner, one of the few GOP Senate candidates who supports marriage equality, is considered a long shot for the nomination.