actually I think he was one upping Kennedy,,his family was Mayflower you know, the Kennedys were new comers. JFK had an entirely different accent, very solid, not a bit pretentious, it was real Boston. Kerry was a poseur even then. I don't think Kerry ever had an identity. He has been on the longest identity quest ever.
I see your point, but I heard it as an overstated JFK accent. I agree JFK had a real accent, but it was a Cape of Cod accent but trained in Haavard Yaard.
Teddy has the true Kennedy (hic up) accent (hic up)... Blub blub blub.
BTW I live in the area, and nobody speaks that way here anymore, except on the Cape.