The Supreme Court’s voting-rights decision Thursday — that Alabama’s Republican-led legislature drew congressional districts that unlawfully diluted the political power of Black voters — shocked the legal and political worlds because of what had come before.

Under Chief Justice John G. Roberts Jr., the court had a nearly unbroken record of weakening the protections of the landmark Voting Rights Act. But Roberts’s majority opinion Thursday maintained the court’s precedents regarding states’ obligations to create electoral districts in which minority voters have a shot at electing candidates of their choice.

With the Roberts court, the status quo was considered a win by civil rights groups who had braced for another setback. That’s because under Roberts, the court has consistently sided with states in saying even the threat of election fraud can justify voting restrictions that often fall heavier on minority voters.

And the justices had already taken two big swings at the Voting Rights Act.

In one, they ruled that state and localities that discriminated against minority voters in the past no longer must have election laws cleared by federal officials.

And in the other, the court said the threat of election fraud can justify voting restrictions that could fall heavier on minority voters. Such decisions have favored conservative states with Republican majorities, while civil rights organizations have been the losers.

Additionally, Roberts said federal courts have no constitutional role in policing partisan gerrymandering. While both parties benefit, it has been Republicans who have said courts should stay out.

Thursday’s decision in Allen v. Milligan, by contrast, will favor Democrats, who benefit from the creation of “majority-minority” districts.

The opinion was particularly significant because it was authored by Roberts, whose aversion to race-based political remedies is well-known.

At his confirmation hearings in 2005, senators questioned memos that Roberts wrote as a young lawyer in the Reagan administration objecting to racial considerations and arguing that it should not become “too easy to prove” certain violations of the Voting Rights Act.

Just months later, in a congressional redistricting case, the new chief justice offered a partial dissent that included what remains one of his most quoted assertions.

“It is a sordid business, this divvying us up by race,” Roberts wrote in League of United Latin American Citizens v. Perry.

Justice Clarence Thomas recalled the quote in his dissent from Thursday’s decision, which lamented a lost chance to junk the court’s precedents about the Voting Rights Act and how it relates to drawing electoral maps. Thomas seemed to wonder what had changed for the chief justice.

“By making it clear that there are political dividends to be gained in the discovery of new ways to sort voters along racial lines,” Thomas wrote, “we prolong immeasurably the day when the ‘sordid business’ of ‘divvying us up by race’ is no more.”

Here is a look at some of the most consequential decisions that the Roberts court has made on voting rights over the past 15 years:

1. Crawford v. Marion County Election Board, 2008

Issue: Indiana’s strict voter identification requirement

Decision: The court said states can require voters to show photo identification before voting, upholding Indiana’s ID requirement, which the Republican-led legislature said was needed to combat voter fraud. Democrats had challenged the law, saying many poor and elderly people were less likely to have the necessary ID, and that the law was designed to discourage voters who lean Democratic.

Majority: The lead opinion in the 6-3 ruling was written by liberal Justice John Paul Stevens, who was joined by Roberts and Justice Anthony M. Kennedy in finding that the law did not violate the Constitution. Justices Clarence Thomas, Samuel A. Alito Jr. and Antonin Scalia agreed with the outcome but would have made it more difficult to challenge similar laws in the future.

Dissent: Liberal Justices David Souter, Ruth Bader Ginsburg and Stephen G. Breyer. Souter wrote that the law threatens to impose “nontrivial burdens on the voting rights of tens of thousands of the state’s citizens and a significant percentage of those individuals are likely to be deterred from voting.”

Worth noting: After his retirement in 2010, Stevens referred to the ruling as a “fairly unfortunate decision,” and expressed doubt about whether he had all the information he needed to decide the case.

2. Shelby County v. Holder, 2013

Issue: Shelby County, Ala., argued that Sections 5 and 4(b) of the Voting Rights Act were unconstitutional. Section 5 required jurisdictions with a history of discrimination to have any election law changes approved in advance by either the Justice Department or federal judges. Section 4(b) was the formula designed by Congress to decide which jurisdictions were covered by what is called preclearance.

Decision: The court struck down Section 4(b) as offensive to the “equal sovereignty” of the states and based on “40-year-old facts having no logical relationship to the present day.” The court did not rule on the constitutionality of Section 5, but without a list of covered jurisdictions, it became unenforceable.

“Our country has changed, and while any racial discrimination in voting is too much, Congress must ensure that the legislation it passes to remedy that problem speaks to current conditions,” Roberts wrote.

Majority: Roberts, Scalia, Kennedy, Thomas, Alito

Dissenters: Ginsburg, Breyer, Sonia Sotomayor (who replaced Souter when he retired in 2009), and Elena Kagan (who replaced Stevens when he retired in 2010). The dissent said the reason conditions have improved is because the preclearance process stopped discriminatory election laws before they could be implemented. “Throwing out preclearance when it has worked and is continuing to work to stop discriminatory changes is like throwing away your umbrella in a rainstorm because you are not getting wet,” Ginsburg wrote.

3. Husted v. A. Philip Randolph Institute 2018

Issue: Purging voter rolls

Decision: The court upheld Ohio’s method of purging infrequent voters from the rolls, a process that challengers said disproportionately affects poor and minority voters.

Majority: Roberts, Kennedy, Thomas, Alito, Neil M. Gorsuch (who joined the court in 2017, filling the vacancy created by Scalia’s death the previous year). Federal law prohibits removing voters simply because they failed to vote. But it also calls on states to keep accurate rolls and allows them to come up with their own systems for removing voters believed to have moved or died.

“We have no authority to second-guess Congress or to decide whether Ohio’s [law] is the ideal method for keeping its voting rolls up to date,” Alito wrote. “The only question before us is whether it violates federal law. It does not.”

Dissent: Ginsburg, Breyer, Sotomayor, Kagan. They said Ohio’s practice violated the prohibition against removing voters because they did not vote.

“Communities that are disproportionately affected by unnecessarily harsh registration laws should not tolerate efforts to marginalize their influence in the political process, nor should allies who recognize blatant unfairness stand idly by,” Sotomayor wrote in a separate dissent.

4. Abbott v. Perez 2018

Issue: Did the Texas legislature discriminate against Black and Latino voters in drawing electoral maps.

Decision: The court largely upheld Texas congressional and legislative maps that a lower court said were drawn to discriminate.

Majority: Roberts, Kennedy, Thomas, Alito, Gorsuch. Although they sided with challengers over one of the legislative districts, the justices said the lower court did not give enough credit to the legislature.

“When all the relevant evidence in the record is taken into account, it is plainly insufficient to prove that the 2013 Legislature acted in bad faith and engaged in intentional discrimination,” Alito wrote.

Thomas, joined by Gorsuch, would have gone further, because of his view that the Voting Rights Act does not apply to redistricting.

Dissent: Ginsburg, Breyer, Sotomayor, Kagan. Sotomayor wrote that the decision “does great damage to the right of equal opportunity.”

“After years of litigation and undeniable proof of intentional discrimination, minority voters in Texas — despite constituting a majority of the population within the state — will continue to be underrepresented in the political process,” she wrote.

5. Rucho v. Common Cause 2018

Issue: Whether the Constitution bars partisan gerrymandering, in which politicians draw electoral districts to preserve or expand their party’s power.

Decision: No, it does not, and federal courts have no role to play in challenges based on partisan gerrymandering.

Majority: Roberts, Thomas, Alito, Gorsuch and Brett M. Kavanaugh (who replaced Kennedy when he retired). “We conclude that partisan gerrymandering claims present political questions beyond the reach of the federal courts,” Roberts wrote. “Federal judges have no license to reallocate political power between the two major political parties, with no plausible grant of authority in the Constitution, and no legal standards to limit and direct their decisions.”

Dissent: Ginsburg, Breyer, Sotomayor, Kagan. Kagan wrote that partisan gerrymanders “imperil our system of government. Part of the court’s role in that system is to defend its foundations. None is more important than free and fair elections.”

6. Brnovich v. Democratic National Committee 2021

Issue: Do certain Arizona election law provisions violate Section 2 of the Voting Rights Act, which forbids discrimination in state and local elections laws?

Decision: No. The justices concluded that the two provisions were directed at preventing election fraud and not at minority voters.

Majority: Roberts, Thomas, Alito, Gorsuch, Kavanaugh, Amy Coney Barrett (who replaced Ginsburg after she died). Fraud can “undermine public confidence in the fairness of elections and the perceived legitimacy of the announced outcome,” Alito wrote. His decision set out multiple factors for evaluating election laws, including the burden on voting created by the rule in question and how much it impacts minority voters as opposed to all in the electorate.

Dissent: Breyer, Sotomayor, Kagan. Kagan again wrote a slashing dissent, saying the new rules had no basis in the text of the law, and further diminished the protections of the Voting Rights Act. “What is tragic here is that the Court has (yet again) rewritten — in order to weaken — a statute that stands as a monument to America’s greatness, and protects against its basest impulses,” she wrote. “What is tragic is that the Court has damaged a statute designed to bring about the end of discrimination in voting.”