Given your reference to “the moderate wing” of the GOP, I assume you think there is an existing moderate wing, but is there? At least the title of this recent book (haven’t read it, just a review of it) would suggest otherwise.
Also see “The losing parties: out-party national committees, 1956-1993” (Yale UP 1994) by Phil Klinker. Klinker asks how losing parties respond to presidential elections.
Before buying into Fig 4-1, I would want to look closely at how Cohen et al measure “ideological extremism.” At least a couple of the placements look odd to me, e.g., McGovern in 72 was, according to the figure, more ‘extreme’ than Goldwater in 64. That seems to me, as an admittedly non-objective observer and one who remembers the 72 campaign very well, to be highly questionable.
Speaking from the point of view of someone who follows the UK’s Conservative Party pretty closely, this is fascinating stuff. It raises the question of whether, when party members (elite and otherwise) regard electoral defeat as inevitable, there’s a part of them that would actually prefer to go down to that defeat with the leader they like least in place – on the assumption that it will put them in a better position to get the leader (and the policies) they really want next time round. I found an undercurrent of that among Tory moderates in the late nineties and early noughties, and it was certainly the case for the Labour Party (or at least the moderates in it) in the early eighties.