My husband has been unfaithful. I am thinking of leaving him. We have been together since my daughter was an infant. My 12 year old daughter has not seen or talked to her father since she was three. My daughter has called my husband Dad for 8 years and even uses his last name (not a legal name change). Does my husband have to pay child support in California if I leave him. We both work. My daughters father is deadbeat in and out of jail.

If the step dad never formally adopted your daughter he does not owe any child support legally. Sounds like you are going to have to go after the real dad for the support regardless if he is a dead beat or not in this case.

Normally no, there are some cases made, but in this case you know the birth father.
Do you already have a custody agreement with the birth father,
Do you already have a child support with the bith father.

And why should he pay for children that are not his ?

Or is he willing to pay support if you allow him to visit ?
Since he also does not have any right to visist