A bipartisan group of lawmakers from the House Judiciary Committee, as well as Senate Majority Leader Harry Reid, filed briefs Friday urging the Supreme Court to keep intact a key 1960s-era law in the federal government’s fight against voter discrimination.

Two Republicans — Reps. F. James Sensenbrenner Jr. of Wisconsin and Steve Chabot of Ohio — joined four Democrats in signing an amicus brief in support of upholding a constitutional challenge to the part of the landmark Voting Rights Act that requires all or parts of 16 states with a history of discrimination in voting to get federal approval before making any changes in the way they hold elections.

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The challenge is among the highest-profile cases the court faces this year. “The Voting Rights Act is the crown jewel of civil rights laws.

It protects our most fundamental right — the right to vote,” Mr. Sensenbrenner said. “This law has empowered minorities to participate in the election process, but the threat of discrimination is not yet extinct.”

The four Democrats signing the brief are Reps. John Conyers Jr. of Michigan, Jerrold Nadler of New York, Melvin L. Watt of North Carolina and Robert C. Scott of Virginia.

Mr. Reid, who filed a separate brief, said that while the nation has made significant progress fighting prejudice and discrimination, numerous allegations of voting suppression in the 2012 elections mean the “Section 5” provision in the voting rights law still is warranted.

“If the Supreme Court dismantles this historic civil rights law and overrules the considered judgment of the people’s elected representatives, it will be a tremendous step backwards for freedom and equality in this country,” the Nevada Democrat said.

The advance approval, or “preclearance” requirement, was adopted as part of the 1965 law to give the federal government a potent legal tool to defeat persistent efforts to keep blacks from voting.

Congress in 2006 reauthorized the Voting Rights Act for an additional 25 years. The bill passed the Senate by a vote of 98-0.

But Shelby County, Ala., near Birmingham, which is appealing the requirement, says it has made significant progress in combating voter discriminate and no longer should be forced to live under oversight from Washington.

The county also argues the law is an encroachment on state sovereignty.

The Supreme Court is scheduled to hear the case Feb. 27. The high court considered the same issue three years ago but sidestepped what Chief Justice John Roberts then called “a difficult constitutional question.”

* This article was based in part on a wire service report.