Re-districting and gerrymandering Redistricting is the process of drawing district boundaries in the States. Every state has a specific amount of district, which mostly depends on population and size. This number can change every ten years by the census. Gerrymandering is the manipulation of the division between districts in order to benefit a party. A good example of gerrymandering, If in California 60% are Democrats, so 60% of its districts should be Democrats. advantages of congressional incumbents, Congressional incumbents have a lot of advantages once they are elected into office. There reelection rate is very high because they have acquired experience and the trust of the people. Another advantage for the incumbents is gerrymandering.