WASHINGTON (AP) — The Supreme Court appeared ready Tuesday to uphold voting restrictions in Arizona in a key case that could make it harder to challenge a raft of other voting measures Republicans have proposed following last year's elections.

All six conservative justices, appointed by Republican presidents, suggested they would throw out an appellate ruling that struck down the restrictions as racially discriminatory under the landmark Voting Rights Act. The three liberal members of the court, appointed by Democrats, were more sympathetic to the challengers.

Less clear is what standard the court might set for how to prove discrimination under the law, first enacted in 1965.

The outcome could make it harder, if not impossible, to use the Voting Rights Act to sue over legislation that creates obstacles to voting in the name of election security. Such measures are currently making their way through dozens of Republican-controlled state legislatures.

Civil rights group and Democrats argue that the proposed restrictions would disproportionately affect minority voters, important Democratic constituencies.

Democrats in Congress, meanwhile, have proposed national legislation that would remove such security-driven obstacles to voting.

Many of those proposals are being driven by former President Donald Trump's repeated false claims of a stolen election, although state elections officials and judges in state and federal courts found no evidence of significant problems.

The Supreme Court case has strong partisan implications, with Arizona and national Republicans on one side, state and national Democrats on the other.

The Arizona provisions under review were in place for last year's voting. They are a 2016 law that limits who can return early ballots for another person and a separate policy of discarding ballots cast in the wrong precinct.

Both parties used ballot collection in Arizona to boost turnout during elections by going door to door and asking voters if they had completed their mail-in ballots. Voters who hadn't were urged to do so, and the volunteers offered to take the ballots to election offices. Democrats used the process more effectively.

Republicans who control the legislature made a crime of ballot collection, dubbed ballot harvesting by opponents, other than for family members and caregivers. Eighty percent of the state's voters use mail-in ballots or vote early in person.

The federal appeals court in San Francisco found that Black, Hispanic and Native Americans voters were most heavily affected by the new law.

Both Chief Justice John Roberts and Justice Brett Kavanaugh pointed to the 2005 recommendation of a commission chaired by former President Jimmy Carter and the late James Baker to eliminate ballot collection, among other ideas to reduce the chance for election fraud.

Kavanaugh said the recommendation seemed to be the sort of “circumstance that puts a thumb on the scale in favor of the legitimacy of the rule.”

Jessica Amunson, representing Arizona Secretary of State Katie Hobbs in opposition to the restrictions, said the court should not ignore the state's experience with ballot collection.

“Arizona had a 25-year history of literally not a single instance of fraud with ballot collection,” Amunson said on behalf of Hobbs, a Democrat.

Justice Elena Kagan asked a series of questions that seemed to be aimed at other restrictions that could find their way to the court, including reducing time for early voting and eliminating polling places.

Michael Carvin, representing Republicans, said the examples Kagan posited “have never existed in the real world."

Kagan replied that they didn't “seem so fanciful to me.”

The high court's last major Voting Rights Act decision was in 2013, when a 5-4 conservative majority gutted the part of the law that forced state and local governments with a history of discrimination, including Arizona, to get advance approval from the Justice Department or a federal court before making any changes to elections. Roberts wrote the court's opinion.

The current case involves the remaining portion of the law that applies nationwide and still prohibits discrimination in voting on the basis of race.

A decision is expected by early summer.

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Associated Press writer Bob Christie in Phoenix contributed to this report.

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