Rucho v. Common Cause and Baker v. Carr

After each census, state legislatures in most states draw the districts used to elect members of the U.S. House of Representatives. In North Carolina, the Republican-controlled legislature adopted a congressional map in 2016 with the stated goal of keeping a 10–3 advantage for its party in the state's 13 seats. In Maryland, Democratic state leaders redrew a congressional district in 2011 in order to flip it from Republican to Democratic control, moving about 360,000 voters out of the district and about 350,000 new voters in.

Voters in both states sued in federal court, arguing that these partisan gerrymanders were unconstitutional because the maps were designed to weaken the votes of people who supported the other party. Among their claims, the North Carolina voters argued that their map violated the Equal Protection Clause of the Fourteenth Amendment, and voters in both states argued that the maps violated the First Amendment. The districts in each state had equal populations. Lower federal courts ruled for the voters.

In a 5–4 decision, the Supreme Court threw out those rulings and ordered the lawsuits dismissed. The majority held that claims of partisan gerrymandering present political questions beyond the reach of the federal courts. It reasoned that, unlike claims about districts with unequal populations, which courts can measure by counting people, there is no clear and manageable legal standard for deciding how much partisanship in drawing districts is too much. The majority noted that the issue could still be addressed by state courts applying state constitutions, by states that give districting to independent commissions, and by Congress, which the Constitution allows to regulate congressional elections.