ATLANTA — The leading candidates in Georgia’s crowded Republican Senate primary are all claiming the pro-business mantle as they battle each other and chase conservative voters. One of the front-runners, Rep. Jack Kingston of Savannah, pitches his U.S. Chamber of Commerce endorsement as proof of his commitment to the private sector, despite two decades on Capitol Hill. But another contender, wealthy businessman David Perdue, hangs his entire campaign on the argument that voters should elect a former corporate CEO instead of politicians like Kingston, former Georgia Secretary of State Karen Handel or two other congressmen: Paul Broun and Phil Gingrey.