Imagine a combination of Hillary Clinton and Barack Obama, and you’ve got Kamala Harris, the current seat-warming senator from California who, like Obama, is using the World’s Greatest Deliberative Body as a resume-puncher before swiftly moving on to bigger things: the 2020 Democrat presidential nomination. Even as a nobody senator, she’s been the subject of dozens, perhaps scores of speculative stories about her future, so now — lest they build her up too quickly — Politico and other Democrat cheerleaders are cautioning her to get her ducks in order before heading out on the hustings: Kamala Harris has been called...