Wearing a Robert Kennedy Jr campaign T-shirt, Kevin O’Keeffe found there was standing room only as the candidate, introduced as “Bobby Kennedy”, walked on a sunbaked stage decked with hay bales to whoops and applause. “He supports freedom of speech, and he’s questioned the efficacy of the vaccine, which is legitimate at this point,” said O’Keeffe, 52, who works for a telecommunications company in Sioux Falls, South Dakota. “I like his views on foreign policy and keeping us out of the war. He cares about his fellow Americans in a way that a lot of the politicians nowadays I don’t...