A super-PAC backing Jeb Bush is aiming to bolster its efforts in South Carolina by adding a GOP strategist well-known in the state to help out in the final days of a "tight, volatile" primary race, Politico reports.Richard Quinn — a longtime adviser to primary race dropout Sen. Lindsey Graham of South Carolina — is taking on the role of conducting polling for Right to Rise ahead of Saturday's vote in the Palmetto State."This is clearly a tight, volatile race that could produce most any result over the next six days," Quinn wrote to Mike Murphy, the head of the super PAC, Politico reports.Polling by the super PAC shows Donald Trump in first place, with a narrow 26 percent to 24 percent lead over Texas Sen. Ted Cruz, and Bush in third place, with a 12 percent to 11 percent advantage over Marco Rubio, Politico reports.