A new David Perdue ad depicts Congressman Jack Kingston as just another career politician who’s lost his conservative credentials after too many years in Washington.

“They arrive with good intentions. So what happened to Jack Kingston?” starts the 30-second spot.

The two are waging an aggressive battle against each other for the GOP nomination for U.S. Senate. In the ad, Perdue takes aim at Kingston for voting to raise the debt ceiling and his own pay. But he largely blames Washington for leading his opponent astray.

AJC political reporter Greg Bluestein writes it was only “a matter of time until Perdue’s campaign unloaded after a few quiet weeks,” saying the businessman has more resources to add to his war chest.

Republican political strategist Todd Rehm says the spot’s softer tone reflects criticism that Perdue has been too negative.

“David Perdue learned a lesson from the primary that going unrelenting negative can have some downsides.”

However, Rehm says it’s difficult to make the case that Kingston is liberal.

“To call Jack Kingston not as conservative is one thing,” said Rehm. “But to call him a liberal when he had the highest rating from the American Conservative Union is bending the truth to the point of breaking.”

Perdue and Kingston will square off in a runoff election on July 22.

Tags: politics, Jack Kingston, U.S. Senate, David Perdue, election2014