I would guess most adulterers have many other reasons that would exclude the. Like with Kerik it looks like adultery is the least crime --- there was the hiring of illegals, there was the failure to pay taxes on his illegals, some suspicious large and unreported gifts. What adulterer is perfect in every other way? Character counts.
Absolutely. Once a person has crossed that line, it's not so hard to cross the line in other areas. Take a look at these husbands who kill their wives.
There is a psychological pathology to adultery that is sociopathic. Marriage and family are supposed to be the most important relationships we have in life. When you no longer honor that - what do you honor?