To be honest, I couldn't think of any Labour politician from the 70s who even slightly resembled Carter
George Thomas maybe? Even if he was done (as a career politician) by the mid 70s, and even if it's impossible to imagine him winning an internal Party contest for anything (of course they said that about Carter. But that was because Carter was an outsider, which Thomas was certainly not by this point).
Or, heading into deeply bizarre territory, perhaps a more successful Elystan Morgan; certainly someone like that would have a better chance of being successful in an Americanesque political system.
Your '68 is hilariously perfect, by the way.
