Much of Harper Lee's To Kill a Mockingbird explores the complex intersection of "people and politics." More specifically, much of the novel focuses on taking larger political issues (racism, sexism, class inequality) and distilling these issues down to a more personal, individual level. For example, the first part of the novel serves to describe the childhood world of Scout, Jem, and Dill. This world is populated by kind, caring, and personable neighbors. After constructing this seemingly idyllic world, Lee spends the latter half of the novel exploring the hidden prejudices that these neighbors harbor. She does so most prominently in the Tom Robinson case, at which point Scout and Jem's "kindly" neighbors condemn an innocent black man simply because he is black.
In Mockingbird, Lee shows how larger political issues - especially political issues involving racism and prejudice - manifest themselves in a more personal setting. In other words, Lee illustrates how it takes "people" to keep political prejudice alive. Most of the time, Lees shows, these people are not a group of far away bigots who are purely evil; rather, they're our neighbors and our friends, individuals that we care about. By illustrating how political prejudice works on this personal level, Lee delves deeply into the complex nature of being human and living in a community with other, deeply flawed, humans.