His personal life is very much a legitimate objection to his attaining the presidency. It illustrates his character It poses questions as to his steadiness and consistency of loyalty. I love Newt Gingrich but he has some of that same baggage and it points to questions about judgment which is a fairly important quality in a president, wouldn't you say? It was President BJ for whom we were to ignore Character and Morals because of his sterling qualities. His biggest failing was precisely judgment.
If infidelity is disqualifying, scratch McCain off your list.