It is hard to admit our flaws and past mistakes, but in the end those who can admit are the ones who have moved on and are ready to accept responsibility. I would vote for someone who has cheated because they know they were in the wrong and are adult enough to admit it and move on.
I would vote for someone who admitted to marital infidelity. Even though I think marital infidelity is wrong and sends the wrong message to people, I truly believe that people make mistakes, admit them, and learn from their mistakes. What happens to people in their private lives is just that, private. A person should not be judged by an error in judgment.