In a presidential election year, there will, of course, be political biographies. But political biographies for children? This month three children's books about one candidate — Hillary Clinton — hit the shelves. Aimed at a variety of age groups, the books deliver a similar message of female strength, though admittedly one likely to go down easier in Democratic-leaning households. Jonah Winter's picture book "Hillary" (Schwartz & Wade, ages 4 to 8) begins with a slightly tongue-in-cheek overview of history's notably strong women: Queen Elizabeth, Joan of Arc ("she was kind of intense"), Rosie the Riveter, "and now there is Hillary."...