Gerald Ford keeps his promise to not run in the 1976. Nelson Rockefeller seeks the nomination. Does he beat Ronald Reagan? And if he does, wold he have beaten Carter? What would have been the butterflies from a Rockefeller presidency?
Nelson Rockefeller might not have had a very long presidency. He seems to have had heart problems as he died in January 1979 from a heart attack (source). Its unclear if he would have survived it even if he had been President and thus had someone with him to notice his condition more quickly.