ATLANTA — Brad Raffensperger, a Republican candidate for governor in Georgia, said Tuesday there was an “active threat” near a planned campaign event a day after, his campaign said, authorities received a message targeting him. A campaign spokesperson said in a statement that the Clay County Sheriff’s Office in Mississippi received a multipage manifesto Monday and that the front page had a photo of Raffensperger, who is Georgia’s secretary of state, with “boom” written across his face. Police