The National Republican Senatorial Committee is making a hefty ad buy in Atlanta, a sign the race for retiring Sen. Saxby ChamblissClarence (Saxby) Saxby ChamblissLobbying World Former GOP senator: Let Dems engage on healthcare bill OPINION: Left-wing politics will be the demise of the Democratic Party MORE's (R-Ga.) seat is still very much competitive.

The NRSC has spent $2.6 million to begin airing ads next Tuesday through mid-September to help businessman David Perdue (R) in his race against former charity executive Michelle Nunn (D), a Democratic operative tracking the buy tells The Hill.

National Republicans have previously downplayed any concerns that Nunn could give Perdue a tough challenge, but the fact that this is their first independent expenditure of the cycle shows it's still a top race. Still, the move is likely a smart one by the NRSC, as Perdue is low on cash following an expensive primary.

The few public polls since Perdue won the primary have found a close race, though most observers believe the Republican has the edge in the race.

Georgia will be the first state where the NRSC has spent on TV, though it's already made fall reservations in five other states and is helping to pay for ads run by Rep. Tom CottonTom CottonMcCarthy: ‘No deadline on DACA’ DHS chief takes heat over Trump furor Lawmakers see shutdown’s odds rising MORE's (R-Ark.) campaign starting Aug. 17.

—This post was updated at 4:17 p.m.