Substitute: Nixon, Reagan, or either Bush and the sentence is just as wrong.
I will allow that, but it affects both sides roughly equally.
Suppose Vance is nominated. He then has a choice. He can talk like a civil warrior, or do a traditional Labor Day pivot to the center. If he picks the civil warrior route, Vance ramps up GOP turnout, but also convinces fence-sitters to turn out for the Democratic ticket on grounds that four years of crazy* was enough. If Vance imitates being presidential, fence-sitters decide the election is a snooze and turnout declines on both sides.
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* I’m using the word crazy in this swing voter sense:
Personally, I do not see Trump/Vance as crazy, but as a nornie strongmen attempting power consolidation.
^Nixon is the apt comparison, but the GOP ditched him. Reagan and Bush Sr. were not seen as disgraces. Dubya was certainly a key reason why Obama won twice, and he was completely rejected by Trump and is certainly not considered to be a GOP hero.
The next successful Republican will have to reject Trump just as Trump rejected Dubya, but he (almost certainly a he) will have a bigger credibility problem. He can’t be Trump sycophant himself and will have to build an administration out of non-sycophants–which won’t be easy, since they’ve all been sycophants forever at this point.
I think the main factors with Vance will be whether is already president or not (very high chance, in my view) and what he has done as president.
It’s clear that Trump is suffering from dementia or some other form of cognitive decline. I don’t think he is rationally pursuing goals much of the time. In that sense, he’s crazy. Vance is not crazy: he’s just ambitious and amoral and has some severe blind spots.