Could US nullify the Trump Clinton presidential race and go with Kaine and Pence or whoever else?

I know it’s never been done, but could US nullify the Trump Clinton presidential race, (because of what the FBI has done and hasn’t done) and go with Kaine and Pence? How about if Clinton picks kasich or Bloomberg although he didn’t run and Trump would pick let’s say whoever democrat he can live with? Why because each side is thinks the other is a horror for the country.