The night that the Sarum bunch showed up to "get" Tom, Atticus was sitting there with a book and was trying to protect him. One of the men was Walter Cunningham. He has known the Finch family for a long time. While they were there, Scout and the kids ran up and interrupted. That was when Walter gained great respect for Atticus and his family. Walter has children of his own and he wouldn't want them around a bunch of drunk men with guns. However, Atticus was calm and never made a big deal out of what could have happened. He could have held that against Walter, but he didn't. So when he put Walter's cousin on the jury, he thought he might have a shot. Normally, a Cunningham would vote to convict Tom no matter what the evidence. However, he knew that the Cunningham's respected him after that night in front of the jail. He said to his kids that
"once you earned their respect they were for you tooth and nail. Atticus said that he had a feeling, nothing more than a suspicion, that they left the jail that night with considerable respect for the Finches."