Republican U.S. Senate candidate Richard Cash speaks after signing an agreement to support any challenger who gets into a runoff with U.S. Sen. Lindsey Graham in June, on the steps of the Statehouse, Thursday, March 13, 2014, in Columbia, S.C. Six GOP candidates have said they want to take on Graham as he seeks a third term. (AP Photo/Jeffrey Collins)

Republican U.S. Senate candidate Richard Cash speaks after signing an agreement to support any challenger who gets into a runoff with U.S. Sen. Lindsey Graham in June, on the steps of the Statehouse, Thursday, March 13, 2014, in Columbia, S.C. Six GOP candidates have said they want to take on Graham as he seeks a third term. (AP Photo/Jeffrey Collins)