Inside Lincoln, Hans Vollman bears witness to the man’s thoughts, as the president says to himself, “Well, what of it. No one who has ever done anything worth doing has gone uncriticized. As regards the matter at hand (as regards him), I am, at least, above any—” Stopping here, Lincoln closes his eyes.
When Lincoln says, “as regards him,” he refers to Willie, to whom he’s trying to formulate a farewell. The fact that he stops and closes his eyes upon thinking that he can’t be criticized for his son’s death suggests that he feels somewhat responsible for Willie’s illness, as if he’s somehow failed in his duties as a responsible parent.