(WASHINGTON) -- The U.S. Supreme Court is set to hear arguments in its coming term on the legitimacy of a controversial legal theory about who oversees elections and whether that authority has limits.
The “independent state legislature" theory, backed by a group of conservative advocates, contends that state lawmakers have the ultimate power to regulate federal elections. That power of elected representatives, the theory's supporters argue, isn't subject to the traditional restrictions provided by state constitutions, state courts and governors' vetoes.
But the theory, if embraced by the justices in its most extreme application, could have a dramatic impact on how congressional maps are drawn, voting rules are written and more, according to election experts who spoke with ABC News.
The theory could undermine how American democracy works now, these experts said, raising concerns about what it could mean for how the 2024 presidential race and other contests are run.
The concept is at the center of Moore v. Harper, a redistricting case out of North Carolina, and concerns how two key clauses in the U.S. Constitution should be interpreted.
The Elections Clause states that “the Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations.”
And the Presidential Electors Clause reads: “Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors."
Jason Snead, the executive director of the Honest Elections Project, a conservative-aligned group which filed an outside amicus brief in Moore v. Harper supporting the theory, said in an interview in August that the issue gets to "the very core of what it is to have a free election."
“If the Supreme Court comes down with a ruling that says, in fact, the word 'legislature' means legislature, I think that’s a win for voters who want fair rules. I would define ‘fair’ as rules written by the people that they elect to write the law,” Snead told ABC News in a separate interview.
But critics of this view say that overstates the intended dominance of one branch of government.
The theory “fixates on the word ‘legislature’ and makes the leap that because the Constitution uses that word, it means to allow a legislature to regulate federal elections absent all those ordinary checks and balances,” said Ethan Herenstein, counsel with the democracy program at the Brennan Center for Justice, an advocacy group and think tank focused on the "values of democracy" and "the rule of law."
The Supreme Court's justices rejected aspects of the "independent state legislature" theory as recently as 2019, when they found that state courts and constitutions could be a check on gerrymandering. But since then, a key number of them have indicated they’re open to exploring the issue again -- though it's unclear if their underlying opinions have changed.
Justice Samuel Alito wrote in an opinion in March that "we will have to resolve this question sooner or later, and the sooner we do so, the better."
“It takes four justices to decide to take a case, so there are at least four justices interested in resolving whether the independent state legislature theory is an appropriate reading of the Constitution, but that doesn’t mean that the court is prepared to adopt this idea,” said Eliza Sweren-Becker, counsel in the Brennan Center's Voting Rights and Elections Program.
At the heart of the dispute in Moore are Republican lawmakers in North Carolina who want to resurrect a congressional map that the state Supreme Court struck down as unconstitutional for violating free speech, free assembly and equal protection provisions of the state constitution. A map approved by a state court was instead put in place for this year's midterm elections.
Here's a breakdown of the possible changes voters and election administrators might experience if the theory were put into practice:
What voters can expect if it's affirmed
Much of what voters deal with when they go to the polls is determined by state and local lawmakers, and most state election laws generally apply to both federal and state elections. States generally have one voter registration system, for example.
But the "independent state legislatures" theory, if sanctioned by the Supreme Court, would allow state lawmakers to rewrite the rules for federal races, including those for president, according to the experts who spoke with ABC News. Any election provision included in the state constitution -- some of which have been adopted through citizen ballot initiatives -- also could be restricted or eliminated completely for federal races.
Mail voting, same-day voter registration, ranked-choice voting systems, secret ballots and other statutes for federal races could be threatened, experts said.
"I think what voters can expect is reduced access to the ballot, more partisan manipulation of maps and more opportunities for partisan interference in elections," said Helen White, a counsel at the nonpartisan group Protect Democracy.
If the theory is affirmed by the court, gerrymandering is also a top concern for the election experts.
The theory, the experts said, would grant authority to state lawmakers to disregard any oversight by state courts -- and gerrymandering could go unchecked.
Snead, whose group is supporting Moore, called such concerns “overblown and overplayed.” State legislatures, he said, would still need to be checked by federal law and Congress.
What election officials can expect
"It would create a two-tiered system where one set of laws applies to federal elections and another set of laws applies to state elections, which were becoming incredibly difficult to administer and be very hard for election officials let alone voters to understand what is required of them," said election attorney Sweren-Becker.
Another likely side effect of the theory being embraced, experts said, would be federal courts becoming inundated with lawsuits about federal election rules because state courts would no longer have a role to play in such issues.
"If anything, the [theory] will promote unending election litigation, bringing uncertainty and disruption," Carolyn Shapiro, a founder and co-director of Chicago-Kent's Institute on the Supreme Court of the United States, told House members in a congressional hearing in late July.
Experts warn elections staff could be overwhelmed and overburdened as a result and congressional maps could become more partisan than ever if state legislatures are allowed to operate with limited constraints -- all of which would disenfranchise and devalue the voice of the voter.
ABC News has reached out to North Carolina House Speaker Tim Moore, who is leading Republicans in the case, for comment but did not receive a response.
In their petition seeking the Supreme Court's review, the attorneys for Moore and the state Republicans wrote that clarity was urgently needed at a local level. They argued that the lawmakers' authority was unduly usurped over concerns about protecting elections.
"The question presented in this case, concerning whether or to what extent a State’s courts may seize on vague and abstract state constitutional language requiring 'free' or 'fair' elections to essentially create their own election code, could scarcely be more significant," the petitioners wrote.
What about presidential electors?
The 2020 election, when some conservatives wanted to create slates of false electors pledged to Donald Trump in states that he had actually lost to Joe Biden, drew national attention to local lawmakers' ability to try and interfere in election results after voting had ended.
The "independent state legislature" theory could bolster future attempts, experts warned.
"This has the potential to change the rules of the game in far-reaching ways in time for the next presidential election," ABC News Political Director Rick Klein said. "Depending on how far the Supreme Court goes, it could virtually invite Republican-controlled legislatures to rewrite centuries-old laws ensuring that the candidate who gets the most votes in a state gets its electoral votes -- and it even could free legislatures to pick electors on their own.”
Snead acknowledged that if the theory is embraced, state lawmakers could decide to pass a law before Election Day that says the legislature is going to set electors rather than the voters.
But experts -- Snead included -- agreed that the theory doesn’t allow a legislature to retroactively change the rules if they don’t like the outcome of the election. The lawmakers would have to still have to enact such changes before the election.
"The independent state legislature is not a license to coup," Sweren-Becker said.
Federal law, she said, prohibits state legislatures from overturning the results of elections.