For all of his flaws, McCain at least wanted the appearances of a fair election without going into the mud. He didn’t tolerate people going for the racist angle. When some stupid lady in the crowd called Obama an Arab, he corrected her (in a sort of racially insensitive way, but…)
Same with Romney. Both of them wanted everyone to think that they were honest people whether they were or not. They cared about their reputations and their legacy.
Trump and his acolytes couldn’t give less of a shit. It’s all about short-term gains.