One day each month, Charlie Kirk, one of the country’s most influential Republican activists, holds an event called Freedom Night in America at Dream City Church, a Pentecostal megachurch on the outskirts of Phoenix. “I truly believe that God has voted early in this election,” he said on a Wednesday in early October, addressing well over 1,000 people from a stage bathed in red, white and blue lights. “I believe that God voted early on July 13, when he spared the life of Donald Trump.” Kirk was only 18 when he helped found the group Turning Point as a sort...