In 1812, the Boston Gazette published an editorial cartoon in response to a redistricting plan signed into law by Massachusetts Governor Elbridge Gerry. The cartoon depicted a portion of Essex County in Massachusetts seemingly haphazardly drawn into a district that would benefit Gerry's Democratic-Republic party. The newly drawn district resembled a salamander, and the artist titled his cartoon "the Gerry-mander." The label stuck and gerrymandering entered the American political vocabulary.
Gerrymandering, the redrawing of electoral district boundaries to favor a particular political group, has its roots in the US Constitution. Article I Section 2 states that members of the US House of Representatives are to be apportioned among the states based on their population as determined every 10 years by census, at a ratio of one Representative for every 30,000 persons. The federal government apportions [PDF] districts among the states based on populations, and then the state legislatures draw the district lines. The Apportionment Act of 1842 established the basic standard that the states divide their territory into individual districts for each representative. In Wesberry v. Sanders, the US Supreme Court held that in the context of apportionment "as nearly as is practicable one man's vote in a congressional election is to be worth as much as another's" and districts should contain a near-equal population.
Over time there have been three recognized [PDF] types of gerrymandering. State legislatures redraw lines in order to favor one political party over another through "partisan gerrymandering," to limit the influence of minority populations on elections through "racial gerrymandering," or to favor incumbent representatives through "incumbent gerrymandering." Congress included sections in the Voting Rights Act of 1965 to diminish the effects of racial gerrymandering. Section 2 of the law prohibits redistricting plans that discriminate on the basis of race. In June 2013, however, the Supreme Court struck down Section 4 of the Act, and thus muted Section 5's requirement that certain states redistricting plans be subject to review by the US Attorney General or to lawsuits in federal District Courts for a determination that the plan does not discriminate.
The court explored a variety of gerrymandering issues in the context of North Carolina's 12th Congressional District. In Shaw v. Reno, the court held that state citizens had a valid claim under the Equal Protection Clause when they alleged that the state deliberately segregated voters into districts based on race and remanded the issue to the District Court. In Shaw v. Hunt, the Court examined the District Court's finding that North Carolina engaged in racial discrimination when it redrew the 12th District and held that the redistricting was invalid because it was not narrowly tailored to serve a compelling interest. Finally, in Hunt v. Cromartie, the court stated that a "jurisdiction may engage in constitutional political gerrymandering, even if it so happens that the most loyal Democrats happen to be black Democrats and even if the State were conscious of that fact."
The House of Representatives consists of 435 members who represent proportional electoral districts of about 700,000 constituents each. Most state legislatures set those district boundaries. Notably, redistricting does not affect US Senate elections, which are statewide. Partisan state legislatures continue to employ redistricting in the hopes that it will send members of their preferred party to Congress. State legislatures also redraw districts to favor incumbents. According to a May 2005 report [PDF] published by The Reform Institute, only five incumbent members running for reelection in 2004 were defeated. Out of 435 seats, 401 Representatives sought re-election and 99% retained their seats. There is debate that, over time, Republican-controlled state legislatures have more frequently engineered outcomes where the number of elected Representatives does not reflect the popular vote.
Republicans in the House of Representatives currently hold a majority, even though they received fewer total votes nationally than House Democrats in the 2012 election and political observers have attributed this result to redistricting. Election data show that in most states where Republicans controlled the redistricting process, Democrats received a low proportion of House seats when compared to the percentage of votes for US President Barack Obama. This implies that Democratic votes are being undercounted in Congressional elections due to redistricting.
Some state legislatures directly passed legislation defining new congressional district boundaries after the 2010 Census. In May 2011, Texas passed a bill redefining [PDF] congressional districts. The state's redistricting plans have been subject to ongoing legal challenges. In December 2011, Pennsylvania's state legislature also passed a redistricting bill.
Even though some state legislatures were quick to pass redistricting measures, other states have employed different approaches. For example, in Iowa, the nonpartisan Legislative Services Agency draws [PDF] neutral, population-based districts after every census. In California, voters approved Proposition 20, which created a redistricting commission tasked with neutrally redrawing congressional districts.
The modern implications of redistricting methods are heavily debated. The current system in many states of having single-party controlled legislatures create the districts has led to strong criticism. Many observers cite this as one of the primary reasons for the increasing partisanship within government, both federally and in the individual states.
Following the 2010 U.S. Census, states were tasked with redistricting based upon the new demographics. Many states have created districts that are heavily saturated by one ideology, making it more difficult for the opposition minority party to challenge for increasingly secured seats. Olympia Snowe, a former Republican Senator from Maine, has been a vocal critic of this through her organization, the Bipartisan Policy Center. She argues that this makes it so that members of Congress lack accountability for their actions because they know there is not a large enough population to challenge their seat in their home district.
Several attempts to overhaul the redistricting process have been introduced with limited success. Notably, John S. Tanner, a Democrat and former U.S. Representative for Tennessee's 8th congressional district, introduced a bill in 2009 that would establish independent, bipartisan commissions to redraw congressional district lines. Under the Tanner proposal, these commissions would do a party-blind redistricting of the state based solely upon county lines, population and straight lines. Other members of congress have introduced similar legislation in 2011 and 2013, with minimal success.
Some states have adopted a process similar to the Tanner proposal. The National Conference of State Legislatures reports that twelve states have fully removed first and final authority for legislative redistricting from the legislature. Six of these have handed the responsibility to a commission not unlike the one Tanner attempted to push through Congress.
Organizations, including the Bipartisan Policy Center, FairVote.org and the USC Annenberg Center, have worked to educate the public and policy makers on the important role redistricting plays in elections. While these various organizations disagree in many ways on an approach, they all agree there is a problem. As many of the organizations point out on their web site, David Winston, the man responsible for drawing the House districts for the Republican party following the 1990 Census, is famous for a comment he made before Congress; "As a mapmaker, I can have more of an impact on an election than a campaign or the candidate."