The US Constitution leaves management of elections to the states; the state legislative houses draw up the district boundaries based on the decennial census, typically to the advantage of the majority party at the time. Some states have been dragged into court for blatant gerrymandering to maximize their party's representation across those districts, with mixed results. In some states, the problems left behind by racial discrimination mean the boundaries must be vetted by the Feds to ensure minorities have a fair shake at the polls.