Answer: Gerrymandering is a problem for the United States House of Representatives.
Explanation/context:
Senators are elected by a whole state's population. The two members of the US Senate from each state are voted into office by the same ballot for all voters in the state.
The House of Representatives is different, however. The number of Representatives per state are based on state population, and district lines are drawn to determine the region of each state which an elected Representative represents.
The landmark case regarding voting district lines was <em>Baker v. Carr </em>(1962), which pertained to voting districts in Tennessee. The plaintiff, Charles Baker, argued that voting districts, which had not been redrawn since 1901, heavily favored rural locations over urban centers which had grown significantly since then. Joe Carr was Secretary of State for Tennessee at the time, so was named in the case in regard to voting district lines as drawn by the state legislature. The Supreme Court ruled that voting districts were not merely a political matter to be decided by legislatures, but that they were subject to review by federal courts to determine their fairness.
The matter of redrawing district lines has come up in court cases again recently as some state legislatures, when dominated by one political party, have "gerrymandered" district lines to try to maintain continued prominence for their party. Legislatures dominated by one party may redraw district lines (following the US Census) in ways that favor their party's candidates maintaining an advantage.
