Metaphor is a figure of speech which makes an implicit, implied or hidden comparison between two things that are unrelated but share some common characteristics. In other words, a resemblance of two contradictory or different objects is made based on a single or some common characteristics.
GHWB, Carter, and Clinton were members of the Trilateral Commission. Both Bushes were members of Skull and Bones. Gingrich wasn’t speaking metaphorically.