What does Atticus have to lose by defending Tom Robinson in To Kill a Mockingbird by Harper Lee?
Atticus has his good standing with the white community to lose. His business may be lost, and his political position in Montgomery taken from him.
When the leading townsmen stand in the Finch yard on the Sunday before the Tom Robinson is moved to the jailhouse, they have come to warn Atticus about the Old Sarum bunch. Atticus tries to allay their fears, but Link Deas says to Atticus,
'--don't see why you touched it in the first place,...You've got everything to lose from this Atticus. I mean everything. (Ch. 15)
Before the trial begins, the Idler's Club sits outside the courthouse and speak of the forthcoming trial. One of them comments, "...thinks he knows what he's doing." Another objects, "...you know the court appointed him to defend this nigger."
The other retorts, "Yeah, but Atticus aims to defend him. That's what I don't like about it."
Atticus's earnest defense of Tom Robinson is tantamount to acting like a "Yankee." For, in the Jim Crow South of the 1930's no white man defended the actions or supposed actions of a Negro. This is why the jury votes as it does. For Atticus to treat Tom as he would a white man is unheard of in Maycomb. Clearly, Atticus takes a huge risk by following his conscience.
Atticus Finch’s decision to defend Tom Robinson is extremely controversial in Maycomb, Alabama. Atticus is a respected lawyer, and choosing to defend an African American accused of rape puts his reputation at risk. Even the children at the elementary school pick fights with Atticus's daughter, Scout, because her father is defending an African American man.
At the beginning of the trial, Bob Ewell, the victim's father, becomes infuriated when he finds out that Atticus chose to defend Tom Robinson, rather than having the case forced upon him. Atticus brushes off Bob Ewell’s anger, and believes that he has nothing to fear from the man.
Yet Atticus realizes that he has much to lose by defending Tom Robinson. Near the end of the novel, Bob Ewell attempts to murder Atticus’s children, Jem and Scout. Only the intervention of Boo Radley prevents Bob from killing the children. Atticus loses nothing, but he learns a valuable lesson about the power of racism in Southern society: white skin does not protect one against violence.