Japan’s Prime Minister Sanae Takaichi appears to have sidestepped a potentially embarrassing political landmine by publicly backing a close aide accused in media reports of running a smear campaign against her rivals, while stopping short of flatly denying his possible role. The allegations, first reported in weekly tabloid news magazine Shukan Bunshun, claim that members of her own camp produced videos critical of rival candidates during last year’s Liberal Democratic Party leadership race,...