WASHINGTON – The Supreme Court’s conservative justices voiced deep skepticism Wednesday about a section of a landmark civil rights law that has helped millions of Americans exercise their right to vote.

In an ominous note for supporters of the key provision of the Voting Rights Act, Justice Anthony Kennedy both acknowledged the measure’s vital role in fighting discrimination and suggested that other important laws in U.S. history had run their course. “Times change,” Kennedy said during the fast-paced, 70-minute argument.

Kennedy’s views are likely to prevail on the closely divided court, and he tends to side with his more conservative colleagues on matters of race.

The court’s liberals and conservatives engaged in a sometimes tense back-and-forth over whether there is an ongoing need in 2013 for the part of the voting rights law that requires states with a history of discrimination, mainly in the Deep South, to get approval before making changes in the way elections are held.

Justice Antonin Scalia called the law a “perpetuation of racial entitlement.”

Chief Justice John Roberts cited statistics that showed starker racial disparities in some aspects of voting in Massachusetts than in Mississippi. Then he asked the government’s top Supreme Court lawyer whether the Obama administration thinks “the citizens in the South are more racist than citizens in the North?”

The answer from Solicitor General Donald Verrilli was no.

Such questions from the conservative justices largely echoed the doubts they first expressed four years ago in a similar case that ended without resolving the constitutionality of the latest renewal of the voting rights law, in 2006. They questioned whether there remain appreciable differences between the locations covered by the law and those that are not. They also wondered whether there was any end in sight for a provision that intrudes on states’ rights to conduct elections and which was regarded as an emergency response to decades of state-sponsored discrimination in voting, despite the Fifteenth Amendment’s guarantee of the vote for black Americans.

The provision shifted the legal burden and required governments that were covered to demonstrate that their proposed changes would not discriminate. Another part of the voting rights law, not being challenged, allows for traditional, after-the-fact claims of discrimination in voting and applies across the country.

The court’s four liberal justices, including Obama appointees Elena Kagan and Sonia Sotomayor, appeared uniformly to be willing to defer to the decision by Congress that more progress needs to be made before freeing states from the special federal monitoring.

Those justices aggressively questioned Bert Rein, the lawyer representing Shelby County, Ala., in its challenge to the law.

Sotomayor asserted that recent voting rights lawsuits in Alabama suggested that Shelby County has not sufficiently progressed.

“Why would we vote in favor of a county whose record is the epitome of what caused the passage of this law to start with?” Sotomayor asked.