Late at night I switch from prose fiction to dvds or graphic fiction. After posting about Poul Anderson's The Boat Of A Million Years, I reread a volume of Hellblazer in which John Constantine meets the dead John Kennedy. I understand that the politician in Chapter XVIIIof Boat is a satire of Kennedy. So that is coincidence or maybe synchronicity.
Fiction reflects reality. Reality includes public figures. Therefore, a politician can appear under a different name in a novel or as a ghost in a fantasy. The present Prince of Wales can become a King without a Parliament in an alternative history. There seem to be no limits to what authors can imagine and readers can accept in works of fiction.