If Republicans succeed in pulling off an aggressively partisan gerrymander of congressional districts in Texas, they will owe the Supreme Court a debt of gratitude.

In the two decades Chief Justice John G. Roberts Jr. has led the Supreme Court, the justices have reshaped American elections not just by letting state lawmakers like those in Texas draw voting maps warped by politics, but also by gutting the Voting Rights Act of 1965 and amplifying the role of money in politics.

Developments in recent weeks signaled that some members of the court think there is more work to be done in removing legal guardrails governing elections. There are now signs that court is considering striking down or severely constraining the remaining pillar of the Voting Rights Act, a towering achievement of the civil rights movement that has protected the rights of minority voters since it was enacted 60 years ago last week.

Taken together, the court’s actions in election cases in recent years have shown great tolerance for partisan gamesmanship and great skepticism about federal laws on campaign spending and minority rights. The court’s rulings have been of a piece with its conservative wing’s jurisprudential commitments: giving states leeway in many realms, insisting on an expansive interpretation of the First Amendment and casting a skeptical eye on government racial classifications.

At bottom, the court’s election-law decisions seem aimed at dismantling decisions of the famously liberal court led by Chief Justice Earl Warren from 1953 to 1969.

In his memoirs, Chief Justice Warren described decisions establishing the equality of each citizen’s vote as his court’s most important achievements. That made them more important in his view even than Brown v. Board of Education, which ordered the desegregation of public schools.

Richard L. Hasen, a law professor at the University of California, Los Angeles, said the Roberts court may be moving in the opposite direction.

“At least some of the conservative justices on the court seem ready to turn the clock back to the early 1960s,” he said, “when courts imposed very little constraints on the most blatant power grabs, and before Congress exercised its constitutional powers to protect voting rights.”

President Trump’s effort to create five additional Republican House seats in Texas, for instance, is possible in part thanks to a 2019 Supreme Court decision that said federal courts have no role to play in assessing the constitutionality of voting maps distorted by politics.

Chief Justice Roberts, writing for the majority in that 5-to-4 decision, Rucho v. Common Cause, acknowledged that “excessive partisanship in districting leads to results that reasonably seem unjust.” Indeed, quoting an earlier decision, he said that drawing voting districts to give the party in power lopsided advantages was “incompatible with democratic principles.”

But in a telling statement reflecting his view of the judicial role in protecting voters, the chief justice wrote that federal courts were powerless to address this grave problem. “Partisan gerrymandering claims,” he wrote, “present political questions beyond the reach of the federal courts.”

In dissent, Justice Elena Kagan said the court had betrayed its most fundamental commitment — to protect democracy.

“These gerrymanders enabled politicians to entrench themselves in office as against voters’ preferences,” she wrote. “They promoted partisanship above respect for the popular will. They encouraged a politics of polarization and dysfunction. If left unchecked, gerrymanders like the ones here may irreparably damage our system of government.”

The Rucho decision was part of a larger trend, said Derek T. Muller, a law professor at Notre Dame.

“These developments reflect a federal judiciary increasingly unwilling to engage in judicial review of the political process,” he said. “And political actors in response are flexing the new power they have.”

The drama in Texas, spurred by Mr. Trump’s desire to bolster Republican chances of retaining control of the House in next year’s midterm elections, caused Democratic lawmakers to leave the state in a bid to stall the plan. The controversy also shows signs of growing into a national fight, with Republican- and Democratic-led state legislatures hatching plans to redraw House maps for partisan advantage.

“We tell ourselves this story that every two years, voters go into the voting booth and pick their member of the House of Representatives,” Pamela Karlan, a law professor at Stanford and a former Justice Department official in Democratic administrations, said on a podcast last week. “And right now it’s the other way around. The politicians are going into a room and picking their voters.”

Writing for the majority in the Rucho case, Chief Justice Roberts said that state courts and independent redistricting commissions still have a role to play in addressing partisan gerrymandering.

At the federal level, though, what remained after Rucho was mostly a part of the Voting Rights Act. It was concerned with discrimination against minority voters and not with partisanship, though race and political affiliations are often hard to untangle.

For nearly 50 years, the central provision of the law imposed federal supervision on states with a history of discrimination, requiring advance approval from the Justice Department or a federal court for all sorts of changes to voting procedures.

The court effectively eliminated that part of the law — its Section 5 — in 2013 in Shelby County v. Holder, by a 5 to 4 vote. That led to a wave of measures making it harder to vote.

But Chief Justice Roberts, again writing for the majority, said the main remaining tool in the Voting Rights Act, its Section 2, remained available. That part of the law allowed for after-the-fact challenges to voting maps that unlawfully diluted minority voting power.

“Section 2 is permanent, applies nationwide and is not at issue in this case,” the chief justice wrote.

Now Section 2 may be in peril, in two ways.

On the last day of the Supreme Court term in June, the justices announced that they would not immediately decide a case from Louisiana testing voting maps that included two majority Black districts to satisfy the Voting Rights Act. A lower court said race had played too large a role in the process, while the state said lawmakers had been motivated by permissible partisan politics.

In an unsigned order in June, the court said it would hear a second argument in the case in the term starting in October.

Such re-arguments are rare, and they can signal that the court is about to convert a routine case into a blockbuster. In 2009, for instance, the court called for a second argument in the Citizens United campaign finance case, turning a minor and quirky case about a movie few had seen into a judicial landmark.

That decision, which allowed unlimited campaign spending by corporations and unions, overturned two precedents and struck down part of a bipartisan 2002 law that sought to limit the role of money in politics.

In their order in June in the new case from Louisiana, the justices said they would pose additional questions “in due course.”

They chose the evening of Friday, Aug. 1 to do so.

The question was a doozy, asking the parties to file supplemental briefs on whether Louisiana’s “intentional creation of a second majority-minority congressional district violates the Fourteenth or Fifteenth Amendments to the U.S. Constitution.”

The question can be read in several ways. But it certainly suggested that the court may consider holding Section 2 unconstitutional.

Section 2 bars any voting procedure that “results in a denial or abridgment of the right of any citizen of the United States to vote on account of race.” That happens, the provision goes on, when racial minorities have less opportunity to elect representatives of their choice than other voters.

Conservative justices have long argued that there is a tension between the statute’s goal of protecting minority voting rights and a colorblind conception of the 14th Amendment’s equal protection clause.

Holding Section 2 unconstitutional could be a boon for Republicans, said Nicholas Stephanopoulos, a law professor at Harvard, as it would allow states to eliminate minority-opportunity districts altogether.

That would make it easy, he said, to draw completely Republican maps in Alabama, Louisiana, Mississippi, South Carolina and elsewhere.

Even if the court stops short of holding Section 2 unconstitutional, it could do great damage to it in another case the court may consider in the term that starts in October. A theory recently adopted by the U.S. Court of Appeals for the Eighth Circuit says that only the government, not voters and other private parties, can sue to enforce the provision.

The Supreme Court paused the Eighth Circuit’s ruling last month, but it may well agree to hear a promised appeal in the coming months, particularly as three members of the court — Justices Clarence Thomas, Samuel A. Alito Jr. and Neil M. Gorsuch — noted dissents.

Accepting the Eighth Circuit’s theory, Professor Karlan said, would cripple the law calling the private right of action “critical to having a V.R.A. at all.”

The controversies over voting rights point to a larger issue about the nature of democracy, said Samuel Issacharoff, a law professor at New York University.

“The majority of today should always fear that it may find itself in the minority tomorrow and that its rules can be used against it,” he said. “What happens when this breaks down? What happens if the majority of today sees this as the last chance to take it all?”