WASHINGTON — There was not much subtlety to the Republicans’ argument to the Supreme Court on Tuesday for allowing laws that effectively limit voting access for people of color.

Overturning a restrictive Arizona law, said Michael A. Carvin, the lawyer representing the Republican Party of Arizona, “puts us at a competitive disadvantage relative to Democrats. Politics is a zero-sum game, and every extra vote they get through unlawful interpretations of Section 2 hurts us,” referring to the part of the Voting Rights Act that is generally used to protect voting access for minority groups.

“It’s the difference between winning an election 50-49 and losing,” he said.

Mr. Carvin’s explanation, in response to a softball question from Justice Amy Coney Barrett about the Republican Party’s interest in a lawsuit brought by Democrats against Arizona, struck at the heart of the latest Supreme Court case that could have a major impact on states’ ability to curtail voting rights.

At issue before the court are Arizona laws forbidding third-party collection of ballots, which Republicans derisively call harvesting, and another requiring election officials to discard ballots cast at the wrong precinct. The broader question is the future of the Voting Rights Act, and whether states will be allowed to restrict voting access unimpeded.

Should the Republican argument prevail at the Supreme Court, where conservative justices hold a six-to-three majority, it could give the party’s lawmakers wide latitude to enact voting restrictions to eliminate early voting on Sundays, end third-party ballot collection and restrict who can receive an absentee ballot — all voting mechanisms Democratic lawyers argued would disproportionately curtail voting access to people of color.

Republicans, in the era of former President Donald J. Trump, have made limiting access to voting a key provision of their political identity. Republicans in at least 43 states are trying to roll back laws increasing access to the ballot box that even some of them had once supported.

In Washington and across the country, Republicans have adopted Mr. Trump’s false claims that the 2020 election was stolen from him, say voters don’t trust the system, and argue, despite numerous studies to the contrary, that easier access to voting inevitably leads to fraud.

While Republican officials have for a generation proffered specious arguments about voter fraud affecting election results, the Trump era marks the first time there has been a party-wide, nationwide effort to limit access to the ballot for people of color and young voters — a population far more inclined to vote for Democrats.

“You can’t build a foundation of lies and then use that foundation to disenfranchise voters, particularly voters of color,” said Tom Perez, the former Democratic National Committee chairman who prosecuted voting rights cases as head of the Justice Department’s Civil Rights Division during the Obama administration. “We’re on really dangerous turf right now when you have Republicans fueling these laws on the basis of falsehoods and the courts are going to be a last resort.”

In this case, the justices have a range of options. They could leave the existing law intact and rule narrowly that the Arizona case was wrongly decided. Arizona’s attorney general and a lawyer for the state’s Republican Party suggested on Tuesday that the court could also choose to exempt some parts of election law — such as a ballot-collection law that deals with how voting is conducted, rather than who votes — from Section 2 coverage.

Or they could rule that a higher standard is needed to show that intentional discrimination or past injustices caused a violation — for example, requiring more substantial evidence of discrimination, or ruling that past discrimination no longer needs to be considered.

Limiting what can be argued under the Voting Rights Act would cut off many legal avenues to challenge new voting restrictions passed by Republican lawmakers.

Last week, Iowa legislators sent to Gov. Kim Reynolds, a Republican, legislation that would cut a third of the state’s early-voting period and lop off an hour of Election Day voting. In Georgia, Republican lawmakers are aiming to sharply limit voting access on Sundays, when many Black voters follow church services with “souls to the polls” bus rides to cast ballots. And in Arizona, Republican lawmakers are backing bills to curtail the automatic mailing of absentee ballots to voters who skip elections, and trying to raise to 60 percent the threshold to pass citizen-led ballot referendums.

Republicans in Pennsylvania and Wisconsin have also pushed for new voting restrictions, though their Democratic governors are certain to veto any such proposals.

The key legal tool in question at the Supreme Court is Section 2 of the Voting Rights Act, which governs after-the-fact challenges to state voting laws. Limiting its application — as the court did in 2013 with the Voting Rights Act’s requirement that some states receive Justice Department clearance before changing voting laws or drawing new legislative maps — could allow states to enact far more sweeping restrictions on voting, while increasing legal hurdles to overturn the new laws.

Section 2 lawsuits have proven pivotal in striking down or modifying restrictions on people’s ability to cast ballots. Among them are a 2015 case overturning Texas’ strict voter ID law and a 2016 decision nullifying a North Carolina voting law, whose constraints ranged from strict ID requirements to limiting voter registration and early voting. In the latter case, an appeals court wrote that Republicans in the state legislature had used the law to target Black voters “with almost surgical precision.”

“It would make it all the harder to stop some of these really dangerous voting laws,” said Stephen Spaulding, a senior counsel for public policy at Common Cause. “It would be an accelerant for further voter suppression.”

Mark Brnovich, the Arizona attorney general who argued the case before the court, said Section 2 can only apply if there is a “substantial” disparity impacting voters of color, a higher standard than Democrats believe exists under the 14th and 15th Amendments. He said that absent the higher bar, Section 2 would “improperly inject race into all voting laws, and impede a state’s ability to run their elections.”

Without the Voting Rights Act, Democrats have few tools to stop Republican-controlled states from limiting voting access.

House Democrats on Wednesday are expected to pass H.R. 1, a bill to standardize federal election rules by overriding many of the restrictive voting laws enacted in the states and to dramatically expand voting access. But the proposal has little chance of proceeding through the Senate unless Democrats there agree to suspend or terminate the filibuster’s 60-vote requirement to pass most legislation.

Though a majority of justices seemed inclined to uphold Arizona’s laws at the end of the nearly two-hour argument on Tuesday, it was not at all clear how broadly their ruling might impact Section 2, the last remaining pillar of the 1965 law, voting-rights experts said.

One big reason is that the law says that whether the section is violated rests heavily on local circumstance, such as whether a law purporting to stop fraud was preceded by actual evidence of fraud. Another is that many violations do not rest on proof of intentional bias — which can be difficult or impossible to prove — but on evidence that the law in question perpetuates old injustices.

The justices appeared on Tuesday to be grappling with how direct that link between an old injustice and a new violation needs to be. For example, a voting literacy test like those of the Jim Crow era might be equally applied to all voters, but it might disproportionately keep minorities from voting because an old injustice — like a segregated school system that gave Black voters a poorer education — caused them to fail. That is a clear link.

But other laws, including the ones in Arizona, may affect minorities disproportionately, yet require a finer judgment as to why. One question in the argument on Tuesday was whether the evidence of intentional bias, including an inflammatory video alleging ballot fraud by Latinos, was sufficient to support a violation.

In striking down the heart of the Voting Rights Act in 2013, the justices effectively said that the federal government no longer could hold veto power over voting laws in states with a history of discrimination because times had changed, and past discrimination in those states no longer was relevant.

“Nobody struck down Section 5,” said Myrna Pérez, who directs the voting rights and elections program at the Brennan Center for Justice, referring to the clause that gave the government veto power known as pre-clearance. “Nobody said it was an overextension of Congress’s power. They just said it didn’t apply.”

Few expect the court to go that far in this case. But a substantial weakening of the standards could make it much harder for plaintiffs to prove that a restriction on voting rights was a violation.

In her closing statement on Tuesday, Jessica Ring Amunson, the lawyer for Katie Hobbs, Arizona’s Democratic secretary of state, urged the court to seek a higher vision of democracy than the “zero-sum” game the Republicans described. The country functions best, she said, when all eligible Americans have the right and access to vote.

“We should actually want to ratchet up participation so that every eligible citizen who wants to vote can do so. Candidates and parties should be trying to win over voters on the basis of their ideas, not trying to remove voters from the electorate by imposing unjustified and discriminatory burdens,” she said.

Speaking of the Republicans, Ms. Amunson concluded: “Unfortunately, petitioners have made clear that that is not their vision of democracy.”