Mr. Barr’s authorization prompted the Justice Department official who oversees investigations of voter fraud, Richard Pilger, to step down from the post within hours, according to an email Mr. Pilger sent to colleagues that was obtained by The New York Times. […] Mr. Barr said he had authorized “specific instances” of investigative steps in some cases. But he made clear in a carefully worded memo that prosecutors had the authority to investigate only “substantial allegations” of irregularities, warning that “specious, speculative, fanciful or far-fetched claims should not be a basis for initiating federal inquiries.” Mr. Barr’s directive ignored the Justice...