A federal prosecutor in Washington has contacted The New England Journal of Medicine, considered the world’s most prestigious medical journal, with questions that suggested without evidence that it was biased against certain views and influenced by external pressures. Dr. Eric Rubin, the editor in chief of N.E.J.M., described the letter as “vaguely threatening” in an interview with The New York Times. At least three other journals have received similar letters from Edward Martin Jr., a Republican activist serving as interim U.S. attorney in Washington. Mr. Martin has been criticized for using his office to target opponents of the administration.His letters...