At 7 p.m. on a cold Thursday night, two SUVs with Maryland plates pull into a CVS parking lot at Florida Avenue and 7th Street NW. Half a dozen men in brightly colored robes emerge and begin to assemble a makeshift pulpit around a black wooden platform. Across the street, the go-go music blasting from a cell-phone store suddenly goes silent. Someone flips the switch on a little generator and two industrial lights flash on, casting a blinding halo around the men gathered by the stage. A tall man in red and gold steps to the mic. His voice booms...