I don't know enough about Spitzer's record as a prosecutor or governor, not being a Noo Yawker, to give him a thumbs up or down on performance. It is unfortunate that his private life had to be exposed.
Some people are better than others at keeping their lives secret.

Eisenhower had a long time mistress, Kay Summersby, who was his driver-secretary, but the press didn't play it up until after he quit the spotlight.
Jesse Jackson fathered a child with his mistress.
Lucy Mercer was F. D. Roosevelt's long time mistress.
John Kennedy had a whole passel of them.
When Newt Gingrich was Speaker, Calista Bisek was his squeeze.
Etc., etc., and so forth.