The Structure of this poem is dominated by the idea of change. The victims mentioned in the title are not only the mother but also her children. They are essentially abused by a domineering man who's bad habits and behaviors ruined their life. However, during the section of the poem where this is described, the speaker is immature and perhaps even naive. This is evident as she makes a comparison between her father and an employee, a very naive comparison. The child in this first section has emotions that seem to mirror her mother's. She "took it and took it" right along with her mother and "pricked with her for years". The speaker is a child and although her father may have been a "slug" of a man she doesn't really comprehend exactly who she is saying these horrible things to. In fact, the poem doesn't mention any actual abuse by the father. All that is mentioned is that he may have been an alcoholic and a workaholic. Both of these are reasons a wife may divorce a husband(though not necessarily good ones), but neither of these are reasons to condemn a man. Nor are they reasons to compare him to Richard Nixon! The reader seems to realize this though, hence the change in tone in line 17.
The moment that the reader identifies the "you" mentioned throughout the poem as her "father", the poem shifts from the angry, possibly naive, child to a mature adult. As an adult, the speaker realizes that she was saying those things about her father, and that deep down she can notice the "underwater fire of their eyes". She is no longer reflective of her mother's emotions, but instead represents her own feelings. This is the change that Olds creates through her clever usage of internal structure, from the naive to the mature.