The "Oswald was impersonated in Mexico City" allegation has been promoted for decades by conspiracy believers - NOT by lone assassin advocates - who say that an Oswald double was sent by the real assassins of JFK, usually it's claimed it was the CIA, to connect Oswald and the assassination to Cuba or the Soviet Union. It was all part of the plan to kill JFK and blame others for some benefit. To justify the removal of Castro, to stop the investigation because it would lead to WWIII, to...well, who knows. They still make the claims today even after all of these revelations indicating it was Oswald and not an impostor.
The claim that this has been a lone assassin issue to use against Oswald is simply wrong from beginning to end. The middle too. It's the conspiracists who have been promoting it. Lone assassin believers have been knocking it down
not promoting it.
Here is an entire section at the Mary Ferrell website where the conspiracy authors claim Oswald was impersonated, where it was part of a CIA drug running operation, where Oswald was with CIA sponsored Phiadelphia Quakers (??) and other craziness:
https://www.maryferrell.org/pages/Oswald_in_Mexico_City.htmlAs for Oswald: This event, his visit, shows that he was willing to completely abandon his pregnant wife and young child, leave them on their own with nothing, defect to a communist country (again) leaving a hated America behind (again), and then behaving like - according to the Cubans and Soviets - an erratic, unstable, paranoid man, a man who said he was being hunted by the US government and that, after pulling out a revolver, saying that if "they don't leave me alone, I'm going to defend myself!"
What does that say about him? To me this is not a well man, he's desperate and angry and unstable. If you think this person was normal, not a danger, then what would it take to prove otherwise?
But again this has been a side argument not a main one: it's been the conspiracists who have obsessed over the Mexico City matter not lone assassin believers.