John McCain didn't save the Republican Party.  It isn't clear that anyone has, but, only Trump and a few allies are trying.  Unless, of course, "Republican Party" means the GOP Establishment, which, together with the Democrat Establishment, has enabled the erosion of American freedom, principles and traditions, in favor of Progressive/Liberalism.
John McCain simply continued to carry out his spiteful campaign against Donald Trump, in retaliation for Trump's thoughtless insult, without any consideration as to the effect on the USA.  
McCain is a hero, but he's  old, and proceeding down a path that  will lead him to be remembered as a mean politician, rather than as a valued public servant.  He should retire, and the Nation should thank him for his service.