A rule by which the design of new electoral boundaries must where possible create electoral districts which have a majority population of some group which is a national minority (hence, majority‐minority districts). In the US, such districts are required by the Voting Rights Act as amended in 1982. Section 2 of the Act includes language designed to prevent dilution of representation for minority groups, and to protect their ability to ‘elect representatives of their choice’, although not a right to proportional representation for protected classes. In Thornburg v. Gingles (1986) the US Supreme Court set out three guidelines for ‘dilution’ which now broadly govern when majority‐minority districts must be created: first, the minority group must be large enough and geographically situated such that a relatively compact district in which they are a majority can be drawn up; secondly, there must be a history of cohesive voting among the minority group; and thirdly, there must be a history of racially cohesive majority voting behaviour sufficient to prevent the election of most of the minority group's favoured candidates.
The creation of majority‐minority districts has had a swift and substantial effect in increasing African‐American representation in the House of Representatives and in state legislatures. It has also been used to create majority Hispanic and Native American districts, especially at the state level. The courts have continued to tinker with the system, concerned that overtly racial drawing of boundaries breaches the Fourteenth Amendment: in Shaw v. Reno (1993) the Supreme Court rejected a North Carolina plan which created an extra majority African‐American district by stringing together a group of geographically dispersed communities along a freeway. Majority‐minority districting in the era since has been controlled by the Court's concerns in that case: district boundaries cannot be drawn solely on the basis of race, as arguably they were in the North Carolina case, but majority‐minority districting can permissibly be part of the entire redistricting scheme, albeit under close judicial supervision. Meanwhile, many supporters of the original scheme have begun to support a move to more proportional, multimember voting systems which may provide a more nuanced tool for increasing minority representation.