Goldwater.
Not because of policies, character, or coalition.
Rather, his inevitable crushing loss, will point out how doomed is that electoral strategy (in Trumps case the inane belief the GOP can still win by driving the white blue collar vote). And thus, the forerunner of a new Tricky Dick who will push for, well, the inverse of the southern strategy.
I can agree with this, but also if you include how the landslide-losing ideology was ushered in in another massive landslide anyway just four cycles later. That's feasibly the direction I see this country going.