Well before Trump came along to validate the conceit, The Walking Dead had added a mordant dimension of political parody to its original survival-of-the-fraughtest premise by introducing David Morrissey as “The Governor,” essentially a psychopath in messiah’s clothing. By now, the series dwells more on rival humanoid factions battling each other than it does on dispatching dull zombies, and the implicit joke is that they’re vying for supremacy in a wasteland that will never again resemble the U.S.A. they once knew. You couldn’t ask for a better preview of next year’s midterm elections.