Mel Wymore is a typical city council candidate in many ways, campaigning as a community board appointee, ex-PTA chair and founder of a roster of local organizations. But Wymore’s community-leader resume has an unusual feature: He built much of it while he was a woman. If he wins, Wymore would be the first openly transgender officeholder in the nation’s biggest city and one of only a handful ever in the U.S., though his campaign isn’t emphasizing his personal story—or sidestepping it. … Wymore, a Democrat, faces several opponents who also have long records of community involvement on Manhattan’s upscale, liberal...