From The Angry Dad:
This is anecdotal evidence, but look at a newspaper advice letter:
Dear Annie: I was with my ex-husband for 18 years before I divorced him. We have three children, and he hasn't been the best father or husband. Lately, however, he has been nice and comes around to visit the kids. I appreciate the fact that he is doing this, but he is now saying things to me that make me uncomfortable.Too nice? No, that is not her problem. She is too mean.
He slept on my couch a couple of nights because he stayed late with the kids when I was out. But now he is coming every day and staying over every night. We often end up sleeping together.
I told him to stop coming around with the expectation that we are getting back together, because we are not. But he refuses to listen, and now he has asked me to marry him again. He won't take "no" for an answer. What should I do? — Think I've Been Too Nice
A lot of women would love to have a man like that. But this one divorced him because of some unspecified imperfections. And now her main complaint is that he loves her and wants to save the family.
If we had a father-custody rule in the USA, divorces like this would not happen.
No, the advice is not to save the marriage. The advice is to limit contact with him and make sure he stays divorced.