What Makes a Cheater Tick?

I can't help it. I just have to comment on Anthony Weiner and Arnold Schwarzenegger. In a way, they are different and the same. But what makes a cheater tick?

Both have pretty and successful wives.
Both are politicians and therefore high profile.
Both are married and are cheaters.
Both were publicly humiliated.

Weiner is (seems) skinny. Schwarzenegger is muscular.
Weiner has no kids (yet). Schwarznegger has 4.
Weiner cheated secretly. Schwarznegger is known to be a womanizer.
Weiner was involved in internet "affairs". Schwarznegger was involved in a  "convenient affair."
Weiner denied when confronted. Schwarzenegger admitted it on his own after years of deception.
Weiner has been married for  about a year. Schwarzenegger has been married for 25 years.

I wonder what their childhood was like...