President Biden again claimed over the weekend that he was detained by South African authorities while trying to visit Nelson Mandela in prison in the 1970s — despite admitting just last month that his telling of the story was false. “I got stopped when I was a young senator trying to see Nelson Mandela in South Africa,” Biden said during a forum broadcast Sunday by left-wing outlet NowThis News. “Afterward he heard, and when he got released, he came to see me in Washington and he walked up to me [and] said, ‘Thank you.'” Biden was responding to Jon-Adrian Velazquez,...