CARTERSVILLE — As they battle for Georgia's Republican nomination for the U.S Senate, Rep. Jack Kingston and businessman David Perdue appeal almost exclusively to conservative voters. That bucks the recent example of Mississippi Sen. Thad Cochran surviving a primary challenge with help from black voters and union members typically aligned with Democrats and, along with Republican Senate primaries Tennessee, South Carolina and elsewhere, serves as a reminder that the GOP's core is still white conservatives, even as party leaders acknowledge the need to widen their appeal in an increasingly diverse nation. Perdue and Kingston meet Tuesday in a runoff to determine who will face Democrat Michelle Nunn in one of the nation's most significant midterm general elections.