Gerrymandering is the practice of setting boundaries of electoral districts to favor specific political interests within legislative bodies, often resulting in districts with convoluted, winding boundaries rather than compact areas. Gerrymandering in the United States has been used to increase the power of a political party; the term "gerrymandering" was coined on review of Massachusetts's redistricting maps of 1812 set by Governor Elbridge Gerry, so named for its resemblance to a salamander.

In the United States, redistricting takes place in each state about every ten years, following the decennial census. This defines geographical boundaries, with each district within a state being geographically contiguous and having about the same number of state voters. The resulting map affects the elections of the state's members of the United States House of Representatives and the state legislative bodies. Redistricting has always been regarded as a political exercise, which in most states is controlled by state legislators and governor. When one party controls the state's legislative bodies and governor's office, it is in a strong position to gerrymander district boundaries to advantage their side and disadvantage their political opponents. Since 2010, detailed maps and high-speed computing have facilitated gerrymandering by political parties in the redistricting process, in order to gain control of state legislation and Congressional representation, and to potentially maintain that control over several decades even against shifting political changes in a state's population.

Accusations of Gerrymandering are rare in the UK since the process of drawing boundaries for electoral districts (constituencies) is done by an independent Boundary Commission BCE. A redrawing in 2023 will slightly favour the Conservative Party- but this is unlikely to be seen as deliberate gerrymandering

Typical gerrymandering cases in the United States take the form of partisan gerrymandering, where the redistricting is aimed to favor one political party or weaken another; bipartisan gerrymandering that is used to protect incumbents by multiple political parties; and racial gerrymandering, aimed at weakening the power of minority voters.

The Supreme Court has failed to settle the issue and left it to the states.

The Supreme Court of the United States has affirmed in Miller v. Johnson (1995) that racial gerrymandering is a violation of constitutional rights and upheld decisions against redistricting purposely devised based on race. However, the Supreme Court has struggled as to when partisan gerrymandering occurs (Vieth v. Jubelirer (2004) and Gill v. Whitford (2018)), and in a landmark decision in 2019 in Rucho v. Common Cause, ultimately decided that questions of partisan gerrymandering represents a nonjusticiable political question that cannot be dealt with by the federal court system. This decision leaves it to states and Congress to develop remedies to challenge and prevent partisan gerrymandering. Some states have created independent redistricting commissions to reduce political drivers for redistricting.

Moore v. Harper  is a pending United States Supreme Court case related to the independent state legislature theory (ISL), arising from the redistricting of North Carolina's districts following the 2020 census. 

In Moore v. Harper, the Supreme Court will decide whether the North Carolina Supreme Court has the power to strike down the legislature’s illegally gerrymandered congressional map for violating the North Carolina Constitution. The legislators have argued that a debunked interpretation of the U.S. Constitution — known as the "independent state legislature theory” — renders the state courts and state constitution powerless in matters relating to federal elections. 

Operation RED MAP

After Obama's election victory in 2008, a group of Republican tacticians developed a plan to increase their chances of winning congressional seats. They targeted Democrat states due to re­draw their house-district boundaries, and concentrated resources to make sure Republicans could take control of the state legislature. After this, new Republican-held state legislatures changed constituency boundaries to maximise Republican success in House of Representative elections.

Political writer David Daley has shown how in various states, such as Pennsylvania, the Republican Party spent significant campaign finance to attack a small number of Democrat state politicians, giving the Republicans a majority that they used to change boundaries for that state. The impact of changing just one state seat from Democrat to Republican was enormous. In 2008, Obama won Pennsylvania and 12 Democrat congressmen won seats from this state. In 2012, Obama won again, but only five Democrats won house elections because the constituency boundaries had changed. In 2012 - the first election using the new maps - Democratic congressional candidates received 100,000 more votes than Republicans, but Republicans won 13 of the 18 seats: 51 per cent of the vote translated into just 28 per cent of the seats. Democrats won by huge margins in just five areas, but more Republicans dominated house elections, with few changes in overall voting patterns.

Merrill v. Milligan October 2022

The Supreme Court is set to hear a case that would maintain Alabama’s discriminatory congressional map and undermine Section 2 of the Voting Rights Act. The plaintiffs and respondents, a group of Black voters and civil rights organizations, claim that the map dilutes Black Alabamans’ voting power. The Brennan Center and partners at Debevoise & Plimpton have filed an amicus brief supporting the lower court’s decision finding the map violates the Voting Rights Act.

Racial Gerrymandering

Alexander v. South Carolina State Conference of the NAACP, 

 Oct 13 2023- The U.S. Supreme Court may be on the verge of making it even harder to win legal challenges accusing state officials of racial gerrymandering - the illegal manipulation of an electoral district's boundaries to alter its racial composition - to dilute the clout of Black and other minority voters. The nine justices this week heard arguments in such a case involving the relocation of 30,000 Black residents from South Carolina's 1st congressional district to another one in an electoral map adopted by the state's Republican-led legislature. The Supreme Court has been asked by the litigants to rule on the legality of the map by the end of the year.

The Supreme Court's conservative justices, holding a 6-3 majority, on Wednesday appeared ready to embrace the argument made by the Republican officials defending the map that it was legally crafted to achieve a partisan advantage and not with a racial motive. 

Associate Justice Neil Gorsuch pushed back against the NAACP’s argument, asking how it can prove South Carolina was acting in bad faith without a map showing the state could accomplish its political goals without using race.

The court will issue a ruling later in the term. 2024

September 2023 the court declined to hear another redistricting case, Robinson v. Ardoin, which concerns Louisiana’s new congressional map. Louisiana will be allowed additional time to consider alternative maps that comply with the Voting Rights Act, instead of immediately holding a hearing to create a remedial map.